Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks.
In the past, the process of choosing a career was a much simpler matter than it is today. Aboy often followed in his father’s footsteps. His sister learned the household skills that (1)..... her to become a wife and mother. Nowadays young people grow up in a much freer society (2)........they enjoy almost unlimited career opportunities. In recent years, there (3)..... an enormous increase in the kinds of vocations from which it is possible to choose. In addition, many of the barriers to career opportunity that existed only a few decades ago, such as (4).......... based on sex or religion or ethnic origins, are (5)............... disappearing.
(2)..................

Read the passage below and choose one correct answer for each question.

Between 1945 and 1973, the economies of the industrialized nations of Western Europe, Japan, and the U. S. grew fast enough to vastly improve living standards for their residents. A similarly favorable growth was registered by some, but far from all, of the developing or industrializing nations, in particular such thriving Southeast Asian economies as Taiwan, Hong Kong, Singapore, and South Korea. After the devastation of World War II, a substantial rebuilding boom, combined with lavish flows of aid from the US, generated rapid growth in Western Europe and Japan. American multinational corporations invested heavily in the rest of the world. Perhaps the most important of all, energy was plentiful and cheap.

Poor nations need aid from the rich nations in the form of capital and of technological and organizational expertise. They also need easy access to the markets of the industrialized nations for their manufactures and raw materials. However, the political capacity of rich nations to respond to these needs depends greatly on their own success in coping with inflation and unemployment. In democratic communities, it is exceedingly difficult to generate public support for assistance to foreign countries when average wage earners are themselves under serious financial pressure. It is not easier politically to permit cheap foreign merchandise and materials to freely enter American and European markets when they are viewed as the cause of unemployment among domestic workers.

After World War II, the US invested a lot in many countries.

No educational medium better as means of spatial communication than the atlas. Atlases deal with such invaluable information as population distribution and density. One of the best, Pennycooke's World Atlas, has been widely accepted as a standard owing to the quality of its maps and photographs, which not only show various settlements but also portray them in a variety of scales. In fact, the very first map in the atlas is a cleverly designed population cartogram that projects the size of each country if geographical size were proportional to population. Following the proportional layout, a sequence of smaller maps shows the world’s population density, each country’s birth and death rates, population increase or decrease, industrialization, urbanization, gross national product in terms of per capita income, the quality of medical care, literacy, and language. To give readers a perspective on how their own country fits in with the global view, additional projections depict the world's patterns in nutrition, calorie and protein consumption, health care, number of physicians per unit of population, and life expectancy by region. Population density maps on a subcontinental scale, as well as political maps. Convey the diverse demographic phenomena of the world in a broad array of scales.

According to the passage, the first map in Pennycooke's World Atlas shows .........

For a time, the Hubble telescope was the brunt of jokes and subject to the wrath of those who believed the U.S government had spent too much money on space projects that served no valid purpose. The Hubble was sent into orbit with a satellite by the Space Shuttle Discovery in 1990 amid huge hype and expectation. Yet after it was in position, it simply did not work. Because the primary mirror was misshapen, it was not until 1993 that the crew of the Shuttle Endeavor arrived like roadside mechanics, opened the hatch that was installed for the purpose, and replaced the defective mirror with a good one.
Suddenly, all that had originally been expected came true. The Hubble telescope was indeed the “window on the universe”, as it had originally been dubbed. When you look deep into space, you are actually looking back through time, because even though light travels at 186,000 miles a second, it requires time to get from one place to another. In fact, it is said that in some cases, the Hubble telescope is looking back eleven billion years to see galaxies already forming. The distant galaxies are speeding away from Earth, some travelling at the speed of light.
Hubble has viewed exploding stars such as the Eta Carinae, which clearly displayed clouds of gas and dust billowing outward from its poles at 1.5 million miles an hour. Prior to Hubble, it was visible from traditional telescopes on Earth, but its details were not as certainable. But now, the evidence of the explosion is obvious. The star still burns five million times brighter than the Sun and illuminates clouds from the inside.
Hubble has also provided a close look at black holes, which are described as comic drains. Gas and dust swirl around the drain and are slowly sucked in by the incredible gravity. It has also looked into an area that looked empty to the naked eye and, within a region the size of a grain of sand, located layer upon layer of galaxies, with each galaxy consisting of billions of stars.
The Hubble telescope was named after Edwin Hubble, a 1920s astronomer who developed a formula that expresses the proportional relationship of distances between clusters of galaxies and the speeds at which they travel. Astronomers use stars known as Cepheid variables to measure distances in space. These stars dim and brighten from time to time, and they are photographed over time and charted. All the discoveries made by Hubble have allowed astronomers to learn more about the formation of early galaxies.

The word “billowing” in the third paragraph is closest meaning to ..........

Choose the word which is stresses differently from the rest: heavy, major, program, reform

The Robots Are Doing the Thinking

Some robots may take care of the dishes, do your laundry, keep the house clean, or even go to the store to do your shopping. Robots that use artificial intelligence are the ones that a lot of people are holding out for. Not only will these robots be able to take care of (1)__________, but they will be able to learn as well.

There are some types of robots that already use a form of artificial intelligence called “swarm intelligence”. As a(n) (2)___________ of how this works, scientists have created underwater robots that will be used to repair coral reefs that have been damaged. What these robots do is work together to rebuild damaged reefs. As they (3)__________, each one knows what has been done in one area of a reef and can help build other areas or build onto something that another robot has done. Working together, the robots create a new reef that can then be (4)__________ to grow and thrive on its own.

Amazon, the major electronic commerce company, has recently come (5)_________ an ingenious idea. Instead of having a package delivered to a customer via delivery truck, Amazon will send out flying drones that will bring a package to a person’s house for delivery almost immediately. 

(3)__________

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks.
              THE FUTURE OF WATER
Many of us often wonder what the future holds; some believe major advances in technology will occur which will result in improvements to our everyday lives. Scientists have predicted shortages in fossil fuels and changes in the weather patterns of the world. (1).......... , one significant change that will have an alarming impact on all of us is the global water shortage. Analysts have forecast that some of the consequences of this will be mass migration from Africa to Europe and wars between countries over clean water. The main causes of this disturbing water shortage are global warming, climate change and the increasing world population. The supply of fresh water (2)....... comes from mountain glaciers and  flows  into  lakes  and  rivers  is  diminishing,  and  this also (3).......... to the shortage. Water analysts and government leaders need to start making radical changes to the way water use is managed and they need to find new sources that will be able to meet the demands of an ever-growing population.  In addition, more things need to be done to control global warming as this will help to reduce water shortages.   People   should   be made  (4)......... of the situation and warned not to waste water. Multinational companies should invest in developing better water management systems. In summary, if we start (5) ............. action now, we might be able to prevent a world disaster.
(1).................................

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Sir Anthony Van Dyck, one of the world’s greatest masters of portraiture, was born in Antwerp and was the seventh of twelve children. His affluent father apprenticed him to a painter when he was just a little over ten. Having become a member of the Antwerp Guild of painters before he was nineteen, he worked in the studio of Peter Paul Rubens for several years. In Italy, Van Dyck studied the great Venetian masters and painted flattering portraits of gorgeous ladies and haughty nobles in gilded velvet robes with lace and pearls. While he was sought after by the aristocracy for his acclaimed loose brushwork, his engravings and etchings also evinced his outstanding talent. Upon his return to Antwerp in 1628, he was influenced by Rubens’s interpretation of the artistic form and produced numerous religious paintings while holding an appointment as the court painter. During his tenure, he proved that his use of color, his sensitive elegance, and his remarkable insight were unexcelled.
His fame preceded him to England, where he was invited by King Charles I. After years of faithful service, he was knighted in recognition of his achievements in painting countless portraits of the king, the queen, the royal children, and the titled nobility of England.
However, Van Dyck’s greatest piece is one of his religious works, a true masterpiece displayed in the Antwerp gallery. This group scene exhibits his artful polish in painting the folds of fabric, the delicacy of human skin, landscape, and other externals, and puts him above other accomplished contemporary masters. Although Charles paid Van Dyck a salary and granted him a pension, the painter’s extravagant life-style and penchant for luxuries led him into debt, and he died without means.

The author of the passage implies that Van Dyck’s fame had largely to do with his

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Line Europeans who arrived in the Americas, the first American Indians were immigrants. Because Indians were nomadic hunters and gatherers, they probably arrived in search of new hunting grounds from Asia when they crossed the ice-covered Bering Strait to Alaska. Anthropologists estimate that the entire Indian population north of Mexico was slightly greater than 1,020,000 when the first settlers arrived from Europe. Although Native Americans belonged to one geographic race, their cultures and languages were only marginally similar, and by and large, they had different ways of life. Nomadic migrations required Indians to construct shelters that did not need to be transported, but could be easily erected from the materials found in their new location.
Eastern Woodland Indian tribes lived in bark-covered wigwams that were shaped like cones or domes. The frame for the hut was made of young trees firmly driven into the ground, and then bent overhead to tie together with bark fibers or strings of animal hides. Sheets and slabs of bark were attached to the frame to construct the roof and walls, leaving an opening to serve as a door and to allow smoke to escape. The Iroquois in north eastern regions built longhouses that were more spacious than wigwams because five to a dozen families lived under one roof. During the winter, they plastered clay to the poles of the frame to protect the inhabitants from wind and rain.
Pueblo Indians who lived in the southwest portion of the United States in northern Arizona and New Mexico constructed elaborate housing with several stories and many rooms. Each family unit had only one room, and their ancestors dug shelters in the walls of cliffs and canyons. The ground story of a Pueblo dwelling had no doors or windows in order to prevent enemies from entering. The next level was set back the width of one room, and the row of rooms above it was set back once again, giving their houses the appearance of a terrace Pueblos used ladders to climb to the upper levels and pulled them in when all family members returned for the night.
Indians living in deserts used sandstone and clay as construction materials. Those who lived in the valleys of rivers even made bricks of clay with wood chips to add strength and to prevent the clay from cracking. To make roofs, Pueblos tied logs together to make rafters and laid them across the two outside walls. On top of the rafters, layers of tree branches, sticks, grass, and brush created a solid roof to preclude the water from leaking inside. Pueblo dwellings were dark because windows were often not large enough to allow much light.

The author of the passage implies that Indians

Millions of people are using cellphones today. In many places, it is actually considered unusual not to use one. In many countries, cellphones are very popular with young people. They find that the phones are more than a means of communication - having a mobile phone shows that they are cool and connected.
The explosion in mobile phone use around the world has made some health professionals worried. Some doctors are concerned that in the future many people may suffer health problems from the use of mobile phones. In England, there has been a serious debate about this issue. Mobile phone companies are worried about the negative publicity of such ideas. They say that there is no proof that mobile phones are bad for your health.
On the other hand, medical studies have shown changes in the brain cells of some people who use mobile phones. Signs of change in the tissues of the brain and head can be detected with modern scanning equipment. In one case, a traveling salesman had to retire at young age because of serious memory loss. He couldn't remember even simple tasks. He would often forget the name of his own son. This man used to talk on his mobile phone for about six hours a day, every day of his working week, for a couple of years. His family doctor blamed his mobile phone use, but his employer's doctor didn't agree.
What is it that makes mobile phones potentially harmful? The answer is radiation. High-tech machines can detect very small amounts of radiation from mobile phones. Mobile phone companies agree that there is some radiation, but they say the amount is too small to worry about.
As the discussion about their safety continues, it appears that it's best to use mobile phones less often. Use your regular phone if you want to talk for a long time. Use your mobile phone only when you really need it. Mobile phones can be very useful and convenient, especially in emergencies. In the future, mobile phones may have a warning label that says they are bad for your health. So for now, it's wise not to use your mobile phone too often.

According to the passage, cellphones are especially popular with young people because  .............

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George Washington Carver showed that plant life was more than just food for animals and humans. Carver’s first step was to analyze plant parts to find out what they were made of. He then combined these simpler isolated substances with other substances to create new products.
The branch of chemistry that studies and finds ways to use raw materials from farm products to make industrial products is called chemurgy. Carver was one of the first and greatest chemurgists of all time. Today the science of chemurgy is better known as the science of synthetics. Each day people depend on and use synthetic materials made from raw materials. All his life Carver battled against the disposal of waste materials and warned of the growing need to develop substitutes for the natural substances being used up by humans.
Carver never cared about getting credit for the new products he created. He never tried to patent his discoveries or get wealthy from them. He turned down many offers to leave Tuskegee Institute to become a rich scientist in private industry. Thomas Edison, inventor of the electric light, offered him a laboratory in Detroit to carry out food research. When the United States government made him a collaborator in the Mycology and Plant Disease Survey of the Department of Agriculture, he accepted the position with the understanding that he wouldn’t have to leave Tuskegee. As an authority on plant diseases – especially of the fungus variety – Carver sent hundreds of specimens to the United States Department of Agriculture. At the peak of his career, Carver’s fame and influence were known on every continent.

The word “step” in paragraph 1 could best be replaced with

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Washington was the first city in history to be created solely for the purpose of governance. Following the Revolution, members of Congress had hotly debated the question of a permanent home for themselves and for those departments – the Treasury, the Patent Office and so on – which even the sketchiest of central governments would feel obliged to establish. In 1790, largely in order to put an end to congressional bickering, George Washington was charged with selecting a site for the newly designated federal district. Not much to anyone’s surprise but to the disappointment of many he chose a tract of land on the banks of the Potomac River, a few miles upstream from his beloved plantation Mount Vernon.
The District of Columbia was taken in part from Virginia and in part from Maryland. At the time it was laid out, its hundred square miles consisted of gently rolling hills, some under cultivation and the rest heavily wooded, with a number of creeks and much swampy land along the Potomac. There is now a section of Washington that is commonly referred to as Foggy Bottom; that section bore the same nickname a hundred and eighty years ago.
Two ports cities, Alexandria and Georgetown, flourished within sight of the new capital and gave it access by ship to the most important cities of the infant nation – Charleston, Baltimore, Philadelphia, New York, Newport, Salem and Portsmouth – and also to the far-off ports of England and the Continent.

The author implies that Georgetown was important in the eighteen century because it

Choose the word or phrase among A, B, C or D that best fits the blank space in the following passage.

We won't have robot doctors for a long time, (1) ____ the human doctors we have now are beginning to learn on specialized artificial intelligence to help save time.

Google Deep Mind has just announced a partnership with University College London Hospital(UCLH) which will explore (2) ____ artificial intelligence to treat patients with head and neck cancers. The goal is to develop tools to automatically identify cancerous cells for radiology machines.

Currently, radiologists employ a manual process, called image (3) ____, to make CT and MRI scans and use them to create a map of the patient's anatomy with clear guidelines of where to direct the (4) ____.

Avoiding healthy areas of the head and neck requires that map to be extraordinarily detailed; typically it takes four hours to create. Google believes it can do the same job or better in one hour.

Deep Mind, Google's research arm, works primarily in deep learning, a form of artificial intelligence that learns to identify patterns from looking at large amount of data. In this case, DeepMind researchers will (5) ____ access to anonymized radiology scans from up to 700 former UCLH patients, and then feed them into (6) ____ that would process the scans to learn the visual difference between healthy and cancerous tissue.

The partnership will (7) ____ researchers to train their algorithms with highly-specialized, high- quality data, which theoretically will enable the algorithm to (8) ____ at a higher rate of success than if they had been using publicly available scans.

For those concerned about machines making health (9) ____ decisions, UCLH made it clear in a statement to the newspaper Guardian that clinicians will be in complete control of diagnoses and treatment.

DeepMind isn't the first care. Samsung Medison, the South Korean (10) ____ company's medical device arm, recently released an ultrasound machine that uses deep learning to quickly recommend whether breast tissue is cancerous or benign. The machine's algorithm was trained on 9,000 breast tissue scans, and is pending FDA approval in the US.

(2) ____

Iron production was revolutionized in the early eighteenth century when coke was first used instead of charcoal for refining iron ore. Previously the poor quality of the iron had restricted its use in architecture to items such as chains and tie bars for supporting arches, vaults, and walls. With the improvement in refining ore, it was now possible  to  make  cast-iron beams, columns, and girders. During the nineteenth century further advances were made, notably Bessemer’s process for converting iron into steel, which made the material more commercially viable.
Iron was rapidly adopted for the  construction  of  bridges,  because  its  strength was far greater  than that of stone or timber, but its use in the architecture of buildings developed more slowly. By 1800 a complete internal iron skeleton for buildings had been developed in industrial architecture replacing traditional timber beams, but it generally remained concealed. Apart from its low cost, the appeal of iron as a building material lay in its strength, its resistance to fire, and its potential to span vast areas. As a result, iron became increasingly popular as a structural material for more traditional styles of architecture during the nineteenth century, but it was invariably concealed.
Significantly, the use  of  exposed  iron  occurred  mainly  in  the  new  building types spawned by the Industrial Revolution: in factories, warehouses, commercial offices, exhibition hall, and railroad stations, where its  practical  advantages  far  outweighed  its  lack of status. Designers of the railroad stations of the new age explored the potential of iron, covering huge areas with spans that surpassed the great vaults of medieval churches and cathedrals. Paxton’s Crystal Palace, designed to house the Great Exhibition of 1851, covered an area of 1.848 feet by 408 feet in prefabricated units of glass set in iron frames. The Paris Exhibition of 1889 included both the widest span and the  greatest height achieved so far with the Halle Des Machines, spanning 362 feet, and the Eiffel Tower 1,000 feet high. However, these achievements were mocked by the artistic elite of Paris as expensive and ugly follies. Iron, despite its structural advantages, had little aesthetic status. The use of an exposed iron structure in the more traditional styles of architecture was slower to develop.

According to paragraph 3, the architectural significance of the Halle Des Machines was its ...........

The attraction of gold is as old as history. Since ancient times, gold has been the object of dreams and obsessions. Western literature is full of characters who kill for gold or hoard it, from King Midas in the ancient Greek myths, to Fagin in Dickens' Oliver Twist. These characters go to evil extremes to get or keep their gold and they get the punishment they deserve. Most people would not be willing to go to such extremes, of course, but they would not question the assumption that gold has lasting value above and beyond any local currency. Societies change over time, customs and currencies evolve, but gold remains. A wedding ring, for example, must be gold, and so should any serious gift of jewelry. In fact, giving and wearing gold is still a mark of prestige in our post-industrial society, though gold is no longer valued as it used to be thousands of years ago.
Why is gold so valuable? True, it is shiny, durable, and rare, but it is far less useful than many other minerals or metals. It is also not like stock in a company, where the value of the stock depends on the performance of the company. Gold, on the contrary, like any currency, is valuable precisely because people believe it is valuable. That is, if people were willing to accept seashells for their labor and could use them to pay for food, fuel, and other commodities, then seashells would become a valuable currency. Thus, the value of gold depends on the collective belief that gold will continue to be valuable. As long as demand for gold remains steady, the price will hold steady; if demand is high, it will continue to increase in value. But if people should someday lose faith in gold, the price of gold could fall sharply.
Another factor that has affected the price of gold has been the increasing difficulty in acquiring it. Today, most of the gold left in the grounds is in microscopic pieces mixed with rock. To get it, miners must dig up tons and tons of rock, and then spray it with chemicals to separate out the gold. For one ounce of gold - a wedding ring, for example - the mine processes about 30 tons of rock. This is already a costly operation. But there are also hidden social and environmental costs. The mining and processing of gold is ruinous to the environment and to the health of people living nearby. Most of these mines are in poor regions where the people have had little voice in whether there should be mines and how the mines should be run. The large multinational mining companies simply bought the land and opened the mines. However, as people and governments begin to realize the extent of the damage caused by the mines, the situation might change.
Indeed, if the mining companies ever have to pay the full environmental and social costs of mining gold, the price of gold is likely to climb yet higher.

The word “it” in paragraph 2 refer to:

Choose the best answer:
When another old cave is discovered in the south of France, it is not usually news. Rather, it is an ordinary event. Such discoveries are so frequent these days that hardly anybody pays heed to them. However, when the Lascaux cave complex was discovered in 1940, the world was amazed. Painted directly on its walls were hundreds of scenes showing how people lived thousands of years ago. The scenes show people hunting animals, such as bison or wild cats. Other images depict birds and, most noticeably, horses, which appear in more than 300 wall images, by far outnumbering all other animals.
Early artists drawing these animals accomplished a monumental and difficult task. “They” did not limit themselves to the easily accessible walls but carried their painting materials to spaces that required climbing steep walls or crawling into narrow passages in the Lascaux complex.
Unfortunately, the paintings have been exposed to the destructive action of water and temperature changes, which easily wear the images away. Because the Lascaux caves have many entrances, air movement has also damaged the images inside. Although they are not out in the open air, where natural light would have destroyed them long ago, many of the images have deteriorated and are barely recognizable. To prevent further damage, the site was closed to tourists in 1963, 23 years after it was discovered.
2.Based on the passage, what is probably true about the south of France?

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Working on the computer is very tough on your body, which is not used to this modem type of work. Sitting has long been known to cause back pain and negatively influence circulation, which can promote cardiovascular disease. Extensive use of the keyboard and mouse can lead to stiffening of the muscles in your hands, arms, and neck. Staring at a bright screen for too long can cause dry eyes and headaches. So, computer work can be as unhealthy a job as you can imagine.
First and foremost, sitting for long stretches of time is a very serious health risk! Sitting affects your blood circulation, your back experiences a steady stress, you are more likely to drink and eat stuff that isn’t good for you, and you bum very little calories, making it more likely that you overeat. As a result, sitting contributes to a host of conditions, most notably gaining weight, diabetes, heart disease, cancer, and consequently a shortened life span.
Second, bad posture causes pain. You can develop bad posture from anything you do habitually, whether it’s sitting, standing, or walking. The typical consequences associated with bad posture while working on the computer are pain in the back, shoulder, and neck, often resulting in tension headaches.
Third, staring at the screen causes eve strain. Staring at a bright screen for hours can lead to eye fatigue or eye strain, headaches, blurred vision, burning, itching or tearing eyes, and temporary vision disorders. Fortunately, eye strain rarely results in a permanent condition and symptoms can be prevented or cured rather easily.
Last, but not least, emotional pressure and isolation cause anxiety and depression. Computers are very efficient tools in that they help us with getting more work done in less time. At the same time, you spend less face-to-face time with your colleagues, family, or friends. This can lead to isolation, anxiety, and depression, i.e. both physical and mental health issues. The symptoms are manifold and can include tense muscles, back pain, headaches, poor sleep (insomnia), increased or flat breathing, quickened pulse, and generally signs of stress, depression, or anxiety.

What is the organization of the passage?

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Living things include both the visible world of animals, plants, and fungi as well as the invisible world of bacteria and viruses. On a basic level, we can say that life is ordered. Organisms have an enormously complex organization. We're all familiar with the intricate systems of the basic unit of life, the cell. Life can also "work." Living creatures can take in energy from the environment. This energy, in the form of food, is transformed to maintain metabolic processes and for survival. Life grows and develops. This means more than just replicating or getting larger in size. Living organisms also have the ability to rebuild and repair themselves when injured. Life can reproduce. Think about the last time you accidentally stubbed your toe. Almost instantly, you moved back in pain. Finally, life can adapt and respond to the demands placed on it by the environment. There are three basic types of adaptations that can occur in higher organisms.
Reversible changes occur as a response to changes in the environment. Let's say you live near sea level and you travel to a mountainous area. You may begin to experience difficulty breathing and an increase in heart rate as a result of the change in altitude. These symptoms go away when you go back down to sea level. Body-related changes occur as a result of prolonged changes in the environment. Using there previous example, if you were to stay in the mountainous area for a long time, you would notice that your heart rate would begin to slow down and you would begin to breath normally. These changes are also reversible. Genotypic changes (caused by genetic mutation) take place within the genetic makeup of the organism and are not reversible. An example would be the development of resistance to pesticides by insects and spiders.

Which of the following is NOT a feature of life?

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What makes it rain? Rain falls from clouds for the same reason anything falls to Earth. The Earth’s gravity pulls it. But every cloud is made of water droplets or ice crystals. Why doesn’t rain or snow fall constantly from all clouds? The droplets or ice crystals in clouds are exceedingly small. The effect of gravity on them is minute. Air currents move and lift droplets so that the net downward displacement is zero, even though the droplets are in constant motion.
Droplets and ice crystals behave somewhat like dust in the air made visible in a shaft of sunlight. To the casual observer, dust seems to act in a totally random fashion moving about chaotically without fixed direction. But in fact dust particles are much larger than water droplets and they finally fall. The cloud droplet of average size is only 1/2500 inch in diameter. It is so small that it would take sixteen hours to fall half a mile in perfectly still air, and it does not fall out of moving air at all. Only when the droplet grows to a diameter of 1/125 inch or larger can it fall from the cloud. The average raindrop contains a million times as much water as a tiny cloud droplet. The growth of a cloud droplet to a size large enough to fall out is the cause of rain and other forms of precipitation. This important growth process is called “coalescence”.

Why don’t all ice crystals in clouds immediately fall to the Earth?

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The ocean bottom - a region nearly 2.5 times greater than the total land area of Earth - is a vast frontier that even today is largely unexplored and uncharted. Until about a century ago, the deep-ocean floor was completely inaccessible, hidden beneath waters averaging over 3,600 meters deep. Totally without light and subjected to intense pressures hundreds of times greater than at the Earth's surface, the deep-ocean bottom is a hostile environment to humans, in some ways as forbidding and remote as the void of outer space.
Although researchers have taken samples of deep-ocean rocks and sediments for over a century, the first detailed global investigation of the ocean bottom did not actually start until 1968, with the beginning ofthe National Science Foundation's Deep Sea Drilling Project (DSDP). Using techniques first developed for the offshore oil and gas industry, the DSDP's drill ship, the Glomar Challenger, was able to maintain a steady position on the ocean's surface and drill in very deep waters, extracting samples of sediments and rock from the ocean floor.
The Glomar Challenger completed 96 voyages in a 15-year research program that ended in November 1983. During this time, the vessel logged 600,000 kilometers and took almost 20,000 core samples of seabed sediments and rocks at 624 drilling sites around the world. The Glomar Challenger's core samples have allowed geologists to reconstruct what the planet looked like hundreds of millions of years ago and to calculate what it will probably look like millions of years in the future. Today, largely on the strength of evidence gathered during the Glomar Challenger's voyages, nearly all earth scientists agree on the theories of plate tectonics and continental drift that explain many of the geological processes that shape the Earth.
The cores of sediment drilled by the Glomar Challenger have also yielded information critical to understanding the world's past climates. Deep-ocean sediments provide a climatic record stretching back hundreds of millions of years, because they are largely isolated from the mechanical erosion and the intense chemical and biological activity that rapidly destroy much land-based evidence of past climates. This record has already provided insights into the patterns and causes of past climatic change - information that may be used to predict future climates.

The author mentions “outer space” because     .

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Washington was the first city in history to be created solely for the purpose of governance. Following the Revolution, members of Congress had hotly debated the question of a permanent home for themselves and for those departments – the Treasury, the Patent Office and so on – which even the sketchiest of central governments would feel obliged to establish. In 1790, largely in order to put an end to congressional bickering, George Washington was charged with selecting a site for the newly designated federal district. Not much to anyone’s surprise but to the disappointment of many he chose a tract of land on the banks of the Potomac River, a few miles upstream from his beloved plantation Mount Vernon.
The District of Columbia was taken in part from Virginia and in part from Maryland. At the time it was laid out, its hundred square miles consisted of gently rolling hills, some under cultivation and the rest heavily wooded, with a number of creeks and much swampy land along the Potomac. There is now a section of Washington that is commonly referred to as Foggy Bottom; that section bore the same nickname a hundred and eighty years ago.
Two ports cities, Alexandria and Georgetown, flourished within sight of the new capital and gave it access by ship to the most important cities of the infant nation – Charleston, Baltimore, Philadelphia, New York, Newport, Salem and Portsmouth – and also to the far-off ports of England and the Continent.

In 1970, a large part of the federal district was     .