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On the tiny island of Flores, east of Bali and midway between Asia and Australia, the scientists have discovered the remains of a small, hobbit-like species of humans. These people grew no larger than the modern three-year-old child. They lived about 18,000 years ago and are completely different species of human.
This discovery has taught scientists a lot about the human species. This remarkable discovery shows that the human species is more varied and flexible in its ability to adapt than previously thought. These hobbit-like people join a short list of other type of humans that lived with modern humans.
The researchers believe that these hobbits evolved from a normal size, human population that reached Flores around 840,000 years ago. One likely explanation is that, over thousands of years, the species became smaller because the environmental conditions favored a smaller body size. The dwarfing of mammals on islands occurs frequently. Islands limit food supply and predators and species compete for the same environmental space. Survival would depend on minimizing energy requirements.a

According to the passage, all of the following can dwarf a species of animal or human except     .

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. 

(2)__________

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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.

It can be inferred from the passage that Pueblo dwellings were designed to protect inhabitants from

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Genetic modification of foods is not a new practice. It has been practiced for thousands of years under the name of "selective breeding". Animals and plants were chosen because they had traits that humans found useful. Some animals were larger and stronger than others, or they yielded more food, or they had some other trait that humans valued. Therefore, they were bred because of those traits. Individuals with those traits were brought together and allowed to breed in the hope that their offspring would have the same traits in greater measure.
Much the same thing was done with plants. To produce bigger or sweeter fruit, or grow more grain per unit of land, strains of plants were combined and recombined to produce hybrids, or crossbreeds that had the desired traits in the right combinations. All the while, however, biologists wondered: is there a more direct and versatile way to change the traits of plants and animals? Could we rewrite, so to speak, the heredity of organisms to make them serve our needs better?
In the 20th century, genetic modification made such changes possible at last. Now, it was possible to alter the genetic code without using the slow and uncertain process of selective breeding. It even became possible to blend plants and animals genetically: to insert animal genes into plants, for example, in order to give the plants a certain trait they ordinarily would lack, such as resistance to freezing. The result was a tremendous potential to change the very nature of biology.

Which of the following IS NOT achieved by genetic modification?

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In young language learners, there is a critical period of time beyond which it becomes increasingly difficult to acquire a language. Children generally attain proficiency in their first language by the age of five and continue in a state of relative linguistic plasticity until puberty. [A] Neurolinguistic research has singled out the lateralization of the brain as the reason for this dramatic change from fluidity to rigidity in language function. Lateralization is the process by which the brain hemispheres become dominant for different tasks. The right hemisphere of the brain controls emotions and social functions, whereas the left hemisphere regulates the control of analytical functions, intelligence, and logic. [B] For the majority of adults, language functions are dominant on the left side of the brain. [C] Numerous studies have demonstrated that it is nearly impossible to attain a nativelike accent in a second language, though some adults have overcome the odds, after lateralization is complete. [D]
Cognitive development also affects language acquisition, but in this case adult learners may have some advantages over child learners. Small children tend to have a very concrete, here- and-now view of the world around them, but at puberty, about the time that lateralization is complete, people become capable of abstract thinking, which is particularly useful for language. Generally speaking, adults can profit from grammatical explanations, whereas children cannot. This is evidenced by the fact that children are rather unreceptive to correction of grammatical features and instead tend to focus on the meaning of  an utterance rather than its form. However, language learning theory suggests that for both adults and children, optimal language acquisition occurs in a meaning centered context. Though children have the edge over adult language learners with respect to attaining a nativelike pronunciation, adults clearly have an intellectual advantage which greatly facilitates language learning.

According to the passage, which of the following is NOT controlled by the left hemisphere of the brain?

Read the following passage and choose the best answer for each blank.

Vietnam is considered a third world country, its people live (26) _____ poverty by the millions. After the (27) _____, Vietnam's economy remained dominated by small-scale production, low labor productivity, (28) _____, material and technological shortfalls, and insufficient food and (29) _____ goods. The Doi Moi reforms that were instated in 1986 have shed new light and added new features to the Vietnamese economy. (30) ____ Vietnamese Communist Party plays a leading role in establishing the foundations and principles of communism, mapping strategies for economic development, setting growth targets, and (31) _____ reforms. Doi Moi combined government planning with free-market incentives and (32) _____ the establishment of private businesses and foreign investment, including foreign-owned enterprises. By the late 1990s, the success of the business and agricultural reforms ushered in under Doi Moi was evident. (33) _____ than 30,000 private businesses had been created, and the economy was growing at an annual (34) _____ of more than 7 percent. Farming systems research and the international development projects are a source of new hope for the people of Vietnam. If these recent projects are successful and Doi Moi continues on its current path the Vietnamese people may (35) _____ a new standard of living. More reforms like Doi Moi need to take place in order to create a more stable Vietnamese future.

(29) _____

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The pain of a migraine headache can virtually disable a person who suffers from it. Millions and millions of people suffer from migraines, although many of them do not even recognize that a migraine is different from a regular headache. A migraine is not at all the same as a normal headache, and it seems to have a very physical cause.
One symptom of a migraine is a precursor, which is a visual aura before an attack. Yet only about a third of patients actually experience that, and it is therefore not a requirement in the diagnosis. Other symptoms include increased pain when a person moves, nausea, and sensitivity to light and sound. Scientists now believe that migraines are caused, not by abnormal blood vessels as previously believed, but instead by a unique electrical disorder of brain cells. Physicians used to treat migraines with medicine to constrict blood vessels because of the belief that dilated blood vessels were the cause.
The new research has been enhanced by imaging devices that allow scientists to watch patients' brains during an attack. The results show that sufferers have abnormally excitable neurons, or brain nerve cells. Prior to the attack, the neurons suddenly fire off electrical pulses at the back of the brain, which ripple like waves on a lake after a stone hits the water. They ripple across the top and then the back of the brain, ultimately affecting the brain stem where the pain centers are located. The pain then generates possibly from the brain stem itself or from blood vessels inflamed by the rapidly changing blood flow, or perhaps from both.
Scientists have experimented by applying a powerful magnet to stimulate the neurons and discovered that some people's brains react differently than others'. When stimulation was applied to the brains of people who had suffered migraines, they saw the initial aura, and some actually suffered migraines. When the same stimulation was applied to the brains of people who had never suffered migraines, they realized no effect and the neurons showed no change.
Scientists and doctors continue to work on the research in an attempt to find the perfect treatment. It is considered important to treat migraines because it is believed that prolonged untreated attacks could cause physical changes in the brain leading to chronic pain.

The author implies that a migraine

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           How the Internet Is Changing Our Language
There are words that we say today that 70 years ago weren’t even in (1)....... . If a person were to remark  to a 1950s businessman, “Go and check this website out on the Internet and get back to me via Facebook,” the businessman would have no clue as to what had just been said. We know exactly what the words mean, though, so they (2)....... perfect sense to us.
The problem that people are encountering today is the same as the 1950s businessman would have encountered - he would have  come (3).....a word that would mean nothing because he lived in a world where Internet technology is changing and progressing today at an even faster (4)........, and this is creating changes in the way we communicate. Our words are different, and even our means of (5)........those words across are different as well. Forget about a 60-plus year difference; we speak much differently than we did even 10 or 20 years ago.
(3).........................
 

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In the exploration of the linguistic life cycle, it is apparent that it is much more difficult to learn a second language in adulthood than a first language in childhood. Most adults never completely master foreign language, especially in phonology - hence the ubiquitous foreign accent. Their development often "fossilizes" into permanent error patterns that no teaching or correction can do. Of course, there are great individual differences, which depend on effort, attitudes, amount of exposure, quality of teaching and plain talent, but there seems to be a cap for the best adults in the best circumstances.
Many explanations have been advanced for children's superiority: they exploit Motherless (the simplified, repetitive conversation between parents and children), make errors oneself- consciously, are more motivated to communicate, like to conform, are not set in their ways, and have no first language to interfere. But some of these accounts are unlikely, based on what is known about how language acquisition works. Recent evidence is calling these social and motivation explanations into doubt. Holding every other factor constant, a key factor stands out: sheer age.
Systematic evidence comes from the psychologist Elisa Newport and her colleagues. They tested Korean and Chinese-born students at the University of Illinois who had spent at least ten years in the United States. The immigrants were given a list of 276 simple English sentences, half of them containing some grammatical errors. The immigrants who came to the United States between the ages of 3 and 7 performed identically to American bom students. Those who arrived between the ages of 8 and 15 did worse the later they arrived, and those who arrived between 17 and 39 did the worst of all, and showed huge variability unrelated to their age of arrival.

What does the word "Those'' in the last paragraph refer to?

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Neil Armstrong started flying at an early age. He became interested in airplanes at the age of 2. At 15, he took flying lessons. He got a license to fly at 16. He learned how to fly before he learned how to drive a car. At university, he studied aeronautical engineering. This is the study of designing and making aircraft.
After Armstrong became an astronaut in 1962, he was trained for 4 years for the Apollo program. The Apollo mission was to put a man on the moon in ten years. On July 16, 1969, the Apollo 11 landed on the moon. Because Armstrong was the leader, he became the first man to step on the moon. He said, "This is one small step for a man, one giant leap for mankind." He and his fellow astronaut, Buzz Aldrin, walked on the moon for two and a half hours. They collected rocks and did some experiments.

According to paragraph 2, which of the following is true about Armstrong's training as an astronaut?

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. 

(5)__________

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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)..................

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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.

What does the passage mainly discuss?

Bees, classified into over 10,000 species, are insects found in almost every part of the world except the northernmost and southernmost regions. One commonly known species is the honeybee, the only bee that produces honey and wax. Humans use the wax in making candles, lipsticks, and other products, and they use the honey as a substance that people eat to maintain life and growth. While gathering the nectar and pollen with which they make honey, bees are simultaneously helping to fertilize the flowers on which they land. Many fruits and vegetables would not survive if bees did not carry the pollen from blossom to blossom.
Bees live in a structured environment and social structure within a hive, which is a nest with storage space for the honey. The different types of bees each perform a unique function. The worker bee carries nectar to hive in a special stomach called a honey stomach. Other workers make beeswax and shape it into a honeycomb, which is a waterproof mass of six-sided compartments, or cells. The queen lays eggs in completed cells. As the workers build more cells, the queen lays more eggs.
All workers, like the queen, are female, but the workers are smaller than the queen. The male honeybees are called drones; they do no work and cannot sting. They are developed from unfertilized eggs, and their only job is to impregnate a queen. The queen must be fertilized in order to lay more worker eggs. During the season when less honey is available and the drone is of no further use, the workers block the drones from eating the honey so that they will starve to death.

According to the passage, honey is carried to the hive in a honey stomach by the.............

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Geothermal energy is natural heat from the interior of the Earth that is converted to heat buildings and generate electricity. The idea of harnessing Earth’s internal heat is not new. As early as 1904 , geothermal power was used in Italy . Today, Earth’s natural internal heat is being used to generate electricity in 21 countries , including Russia, Japan, New Zealand, Iceland, Mexico, Ethiopia, Guatemala, EI Salvador, the Philippines, and the United States .Total worldwide production is approaching 9,000 MW (equivalent to nine large modern coal-burning or nuclear power plants)-double the amount in 1980 .Some 40 million people today receive their electricity from geothermal energy at a cost competitive with that of other energy sources. In EI Salvador , geothermal energy is supplying 30% of the total electric energy used.
However, at the global level, geothermal energy supplies less than 0,15%of the total energy supply.
Geothermal energy may be considered a nonrenewable energy source when rates of extraction are greater than rates of natural replenishment. However, geothermal energy has its origin in the natural heat production within Earth , and only a small fraction of the vast total resource base is being utilized today. Although most geothermal energy production involves the tapping of high heat sources, people are also using the low-temperature geothermal energy of groundwater in some applications.

Geothermal Systems
The average heat flow from the interior of the Earth is very low, about 0,06% W/m2.This amount is trivial compared with the 177 W/m2from solar heat at the surface in the United States. However, in some areas, heat flow is sufficiently high to be useful for producing energy . For the most part, areas of high heat flow are associated with plate tectonic boundaries. Oceanic ridge systems (divergent plate boundaries) and areas where mountains are being uplifted and volcanic island arcs are forming (convergent plate boundaries) are areas where this natural heat flow is anomalously high. One such region is located in the western, United States, where recent tectonic and volcanic activity has occurred.
On the basis of geological criteria, several types of hot geothermal systems (with temperatures greater than about 800C , or 1760F)have been defined, and the resource base is larger than that of fossil fuels and nuclear energy combined. A common system for energy development is hydrothermal convection, characterized by the circulation of steam and / or hot water that transfers heat from depths to the surface.

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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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Martin Luther King, Jr., is well known for his work in civil rights and for his many famous speeches, among them is his moving “I Have A Dream” speech. But fewer people know much about King’s childhood. M.L., as he was called, was born in 1929 in Atlanta, Georgia, at the home of his maternal grandfather. M.L.’s grandfather, the Reverend A.D. Williams, purchased their home on Auburn Avenue in 1909, twenty years before M.L. was born. The Reverend Williams, an eloquent speaker, played an important role in the community since so many people’s lives centered around the church. He allowed his church and his home to be used as a meeting place for a number of organizations dedicated to the education and social advancement of blacks.
M.L. grew up in this atmosphere, with his home being used as a community gathering place, and was no doubt influenced by it.

M.L.’s childhood was not especially eventful. His father was a minister and his mother was a musician. He was the second of three children, and he attended all-black schools in a black neighborhood. The neighborhood was not poor, however. Auburn Avenue was the main artery through a prosperous neighborhood that had come to symbolize achievement for Atlanta’s black people. It was an area of banks, insurance companies, builders, jewelers, tailors, doctors, lawyers, and other black-owner, black- operated businesses, and services. Even in the face of Atlanta’s segregation, the district thrived. Dr. King never forgot the community spirit he had known as a child, nor did he forget the racial prejudice that was a seemingly insurmountable barrier that kept black Atlanta from mingling with whites.

The word “it” in paragraph 2 refers to

Whales are the largest animals in the world, and the gentlest creatures we know. Although the whale is very huge, it is not hindered at all by its size when it is in the water. Whales have tails that end like flippers. With just a gentle flick, it can propel itself forward. The skin of a whale is so smooth that it does not create any friction that can slow the whale down. A whale’s breathing hole is located on the top of its head, so it can breathe without having to completely push its head out of the water. Whales are protected from the cold seawater by body fat that is called blubber.
Whales live in the ocean but, in terms of behaviours, they are more similar to humans than fish. They live in family groups and they even travel in groups when they have to migrate from cooler to warmer waters. The young stay with their parents for as long as fifteen years. Whales are known not to desert the ill or injured members; instead, they cradle them.
When whales are in danger, there are people who go to great lengths to help them. One such case occurred in 1988, when three young whales were trapped in the sea. It was close to winter and the sea had begun to freeze over. Whales are mammals that require oxygen from the air, so the frozen ice was a great danger to them. All they had then was a tiny hole in the ice for them to breathe through. Volunteers from all over soon turned up to help these creatures. They cut holes in the ice to provide more breathing holes for the whales. These holes would also serve as guides for the whales so that they could swim to warmer waters.

The word “tiny” in paragraph 3 probably means ..............

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.

What do many people believe about gold?

Increasing numbers of parents in the U.S. are choosing to teach their children at home. In fact, the U.S. Department of Education has estimated that in 1999, about 850,000 children were being homeschooled. Some educational experts say that the real number is double this estimate, and the ranks of homeschooled children seem to be growing at the average rate of about eleven percent every year.
At one time, there was a theory accounting for homeschooling: it was traditionally used for students who could not attend school because of behavioral or learning difficulties. Today, however, more parents are taking on the responsibility of educating their own children at home due to their dissatisfaction with the educational system. Many parents are unhappy about class size, as well as problems inside the classroom. Teacher shortages and lack of funding mean that, in many schools, one teacher is responsible for thirty or forty students. The children are, therefore, deprived of the attention they need. Escalating classroom violence has also motivated some parents to remove their children from school.
Although there have been a lot of arguments for and against it, homeschooling in the U.S. has become a multi-million dollar industry, and it is growing bigger and bigger. There are now plenty of websites, support groups, and conventions that help parents protect their rights and enable them to learn more about educating their children. Though once it was the only choice for troubled children, homeschooling today is an accepted alternative to an educational system that many believe is failing.

The noun “dissatisfaction” in this paragraph is best equivalent to “   ..........  ”

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.

Iron replaced stone and timber in the building of bridges because iron was considered ..........