Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions:
Rachel Carson was bom in 1907 in Springsdale, Pennsylvania. She studied biology in college and zoology at Johns Hopkins University, where she received her master’s degree in 1933. In 1936, she was hired by the US Fish and Wildlife Service, where she worked most of her life.
Carson’s first book, Under the Sea Wind, was published in 1941. It received excellent reviews, but sales were poor until it was reissued in 1952. In that year, she published The Sea Around Us, which provided a fascinating look beneath the ocean’s surface, emphasizing human history as well as geology and marine biology. Her imagery and language had a poetic quality. Carson consulted no less than 1, 000 printed sources. She had voluminous correspondence and frequent discussions with experts in the field. However, she always realized the limitations of her non-technical readers.
In 1962, Carson published Silence Spring, a book that sparked considerable controversy. It proved how much harm was done by the uncontrolled, reckless use of insecticides. She detailed how they poison the food supply of animals, kill birds, and contaminate human food. At that time, spokesmen for the chemical industry mounted personal attacks against Carson and issued propaganda to indicate that her findings were flawed. However, her work was vindicated by a 1963 report of the President’s Science Advisory Committee.

The passage mainly discusses Rachel Carson’s work         .

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct answer to each of the questions:
The Internet started out as a limited network called the ARPANET (Advanced Research Projects Agency Network). It was a network of computers that allowed communication even if computer became non- functioning. It was the academic and scientific community that adopted Internet, using a protocol called TCP/IP. TCP/IP allows a number of different network computers to be connected together. This is called the Internet. The Internet allows the creation the World Wide Web or the Web for short. The Web consists of Internet sites that allow data to be shared by others. Aside from making the Web possible, the Internet also makes e-mail, chat rom and file-sharing and telephoning possible. It even allows people to watch media and play games.
The Web can be read in a browser. A browser is simply a software program that uses HTTP (Hyper Text Transfer Protocol) data transmission. This will allow you to view Web pages. HTTP let you browser read the text, graphics, animation, video and music that are on the Web page. It also enables you to click on a link on the page using the mouse. The links on a Web page that guide you to go from one Web page to another are called hyperlinks. A Web page usually contains many hyperlinks so that you can “browse” the Internet. It is much like reading a book. You can go from page to page and get new information. One example of a browser is Internet Explorer. In the address box of your browser, you can type in an address called a URL for “uniform resource locator”.
To be able to use the Internet, you must have a computer with an Internet connection and software that lets you view that Web pages. Internet connection is called a dial-up connection. It needs the use of your telephone to connect your computer to an Internet service. A faster type of connection is called broadband. This requires a cable or some other equipment. If you turn on the computer with a broadband connection, it connects you the Internet at a time.

The word “It” in paragraph 1 refer to     .

Attention Students
This Saturday, October 20, is the registration deadline for the winter terns.
Complete your registration form in the Administrative Office on the second floor between the hours of 8:00 a.m. and 5:30 p.m. Payment must be made at the time of registration, so bring your credit card, a money order, or cash with you. Personal cheques will not be accepted. No late exceptions. Classes begin Monday, October 22.

What can be inferred from the announcement?

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions. 
      When we think of the renewable energy transition, we often have in mind dark blue photovoltaic rectangles carpeting the landscape or large three-blade horizontal axis wind turbines marching along mountain ridges or into the sea. We think about grid reliability and consumer cost per kilowatt-hour, or we think about the climate change apocalypse that we will impose on future generations if we fail to act swiftly enough. All of these elements are important from technical and policy perspectives, but there is something missing that will be key to success if we are to meet the goals that we have set for ourselves. We must recognize the importance of human culture to the realization of change.
      It is a lack of imagination that has brought us to the brink, and it will be an influx of imagination that can possibly pull us back from it. If we are going to succeed in reducing carbon emissions, we must make the solutions more visible, inspire the general public, and get people excited about the renewable energy transition.
This is the mission of the Land Art Generator Initiative (LAGI), a nonprofit that works with cities around the world on civic art installations that also function as renewable energy infrastructures. These generous works of art give back more than just beauty and return more than just kilowatt hours on their capital investment. LAGI design competitions have changed the way that cities and developers manage the integration of public art and creative placemaking into the master planning process for new developments. Competitions for Dubai/Abu Dhabi (2010), New York City (2012), Copenhagen (2014), Glasgow (2015), Santa Monica (2016), Willimantic (2017), and Melbourne (2018) have brought in over 1,000 designs from 60+ countries.

The word “it” in paragraph 2 refers to _______.

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions:
Scientists do not yet thoroughly understand just how the body of an individual becomes sensitive to  a substance that is harmless or even wholesome for the average person. Milk, wheat, and egg, for example, rank among the most healthful and widely used foods. Yet these foods can cause persons sensitive to them to suffer greatly. At first, the body of the individual is not harmed by coming into
contact with the substance. After a varying interval of time, usually longer than a few weeks, the body becomes sensitive to it, and an allergy has begun to develop. Sometimes it's hard to figure out if you have a food allergy, since it can show up so many different ways.
Your symptoms could be caused by many other problems. You may have rashes, hives, joint pains mimicking arthritis, headaches, irritability, or depression. The most common food allergies are to milk, eggs, seafood, wheat, nuts, seeds, chocolate, oranges, and tomatoes. Many of these allergies will not develop if these foods are not fed to an infant until her or his intestines mature at around seven months. Breast milk also tends to be protective. Migraines can be set off by foods containing tyramine, phenathylamine, monosodium glutamate, or sodium nitrate. Common foods which contain these are chocolate, aged cheeses, sour cream, red wine, pickled herring, chicken livers, avocados, ripe bananas, cured meats, many Oriental and prepared foods (read the labels!).
Some people have been successful in treating their migraines with supplements of B-vitamins, particularly B6 and niacin. Children who are hyperactive may benefit from eliminating food additives, especially colorings, and foods high in salicylates from their diets. A few of these are almonds, green peppers, peaches, tea, grapes. This is the diet made popular by Benjamin Feingold, who has written the book “Why your Child is Hyperactive”. Other researchers have had mixed results.

What can be inferred about babies from this passage?

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct answer to each of the questions:
Most people can remember a phone number for up to thirty seconds. When this short amount of time elapses, however, the numbers are erased from the memory. How did the information get there in  the first place? Information that makes its way to the short term memory (STM) does so via the sensory storage area. The brain has a filter which only allows stimuli that is of immediate interest to pass on to the STM, also known as the working memory.
There is much debate about the capacity and duration of the short term memory. The most accepted theory comes from George A. Miller, a cognitive psychologist who suggested that humans can remember approximately seven chunks of information. A chunk is defined as a meaningful unit of information, such as a word or name rather than just a letter or number. Modern theorists suggest that one can increase the capacity of the short term memory by chunking, or classifying similar information together. By organizing information, one can optimize the STM, and improve the chances of a memory being passed on to long term storage.
When making a conscious effort to memorize something, such as information for an exam, many people engage in "rote rehearsal". By repeating something over and over again, one is able to keep a memory alive. Unfortunately, this type of memory maintenance only succeeds if there are no interruptions. As soon as a person stops rehearsing the information, it has the tendency to disappear. When a pen and paper are not handy, people often attempt to remember a phone number by repeating it aloud. If the doorbell rings or the dog barks to come in before a person has the opportunity to make a phone call, he will likely forget the number instantly. Therefore, rote rehearsal is not an efficient way to pass information from the short term to long term memory. A better way is to practice "elaborate rehearsal". This involves assigning semantic meaning to a piece of information so that it can be filed along with other pre-existing long term memories.
Encoding information semantically also makes it more retrievable. Retrieving information can be done by recognition or recall. Humans can easily recall memories that are stored in the long term memory and used often; however, if a memory seems to be forgotten, it may eventually be retrieved by prompting. The more cues a person is given (such as pictures), the more likely a memory can be retrieved. This is why multiple choice tests are often used for subjects that require a lot of memorization.

The word “cues” in paragraph 4 is closest in meaning to     .

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct answer to each of the questions:
Deforestation is the clearing, destroying, or otherwise removal of trees through  deliberate,  natural or accidental means. It can occur in any area densely populated by trees and other plant life, but the majority of it is currently happening in the Amazon rainforest. The loss of trees and other vegetation can cause climate change, desertification, soil erosion, fewer crops, flooding, increased greenhouse gases in the atmosphere, and a host of problems for indigenous people.
Deforestation occurs for a number of reasons, including: farming, mostly cattle due to its quick turn around; and logging for materials and development. It has been happening for thousands of years, arguably since man began converting from hunter/gatherer to agricultural based societies, and required larger, unobstructed tracks of land to accommodate cattle, crops, and housing. It was only after the onset of the modern era that it became an epidemic.
One of the most dangerous and unsettling effects of deforestation is the loss of animal and plant species due to their loss of habitat; not only do we lose those known to us, but also those unknown, potentially an even greater loss. Seventy percent of Earth's land animals and plants live in forests, and many cannot survive the deforestation that destroys their homes. The trees of the rainforest that provide shelter for some species also provide the canopy that regulates the temperature, a necessity for many others. Its removal through deforestation would allow a more drastic temperature variation from day to night, much like a desert, which could prove fatal for current inhabitants.
In addition to the loss of habitat, the lack of trees also allows a greater amount  of  greenhouse gases to be released into the atmosphere. Presently, the tropical rainforests of South America are responsible for 20% of Earth's oxygen and they are disappearing at a rate of 4 hectares a decade. If these rates are not stopped and reversed, the consequences will become even more severe.
The trees also help control the level of water in the atmosphere by helping to regulate the water cycle. With fewer trees left, due to deforestation, there is less water in the air to be returned to     the soil. In turn, this causes dryer soil and the inability to grow crops, an ironic twist when considered against the fact that 80% of deforestation comes from small-scale agriculture and cattle ranching.
Further effects of deforestation include soil erosion and coastal flooding, In addition to their previously mentioned roles, trees also function to retain water and topsoil, which provides the rich nutrients to sustain additional forest life. Without them, the soil erodes and washes  away,  causing farmers to move on and perpetuate the cycle. The barren land which is left behind in the wake of these unsustainable agricultural practices is then more susceptible to flooding, specifically in coastal regions. Coastal vegetation lessens the impact of waves and winds associated with a storm surge. Without this vegetation, coastal villages are susceptible to damaging floods.

The word "perpetuate" in the last paragraph is closest in meaning to     _.

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions. 
Astronomers have for the first time definitively ID’d the birth of a specific heavy element during a neutron-star smashup. They found strontium. And it showed up in the wavelengths of light — or spectra — making up this collision’s afterglow.
Scientists had assumed that a collision by two super-dense objects, such as neutron stars, would trigger a chain of nuclear reactions. They’re known as the r-process. In such an environment, the nuclei of atoms could rapidly gobble up neutrons. Afterward, those nuclei would become transformed in a process known as radioactive decay. The r-process was seen as a way to transform old, smaller elements into newer, bigger ones. About half of all elements heavier than iron were thought to be made in the r-process. Finding strontium in the recent collision at last offered the most direct evidence yet that neutron-star collisions really do trigger the r-process.
Physicists had long predicted that silver, gold and many other elements more massive than iron formed this way. But scientists weren’t sure where those r-process reactions took place. After all, no one had directly seen the r-process underway in a celestial event. Or they didn’t until the merger of two neutron stars in 2017. Scientists quickly analyzed light given off by that cataclysm. In it, they found evidence of the birth of a hodgepodge of heavy elements. All would seem to have come from the r-process. 
The researchers were examining mostly very heavy elements — ones whose complex atomic structures can generate millions of spectral features. And all of those features were not yet fully known, Watson points out. This made it extremely difficult to tease apart which elements were present, he says.
Strontium, however, is relatively light compared to other r-process elements. And its simple atomic structure creates a few strong and well-known spectral clues. So Watson and his colleagues expanded their analysis to consider it. In doing so, they turned up the clear "fingerprint" of strontium. It emerged in light collected by the Very Large Telescope in Chile within a few days of the neutron-star collision. Seeing strontium in the afterglow wasn’t all that unexpected, says Brian Metzger. He’s an astrophysicist at Columbia University in New York City and not involved in the new work. Strontium, he notes, “does tell us something interesting” about the elements formed during the neutron-star collision.

The word “it” in paragraph 1 refers to _____.

Read the following passage and mark the letter A, B, C, or D to indicate the correct word or phrase that best fits each of the numbered blanks. 
Do you ever find yourself flustered when you see someone you don't expect? Have you experienced those embarrassing and awkward moments (25) _____ you can't think of something to say? Prepare yourself for the future so you won't be caught off guard. Being prepared can (26) _____ the difference between feeling self-conscious and being confident as you express your delight (27) _____ seeing someone you know.
When you're out and about, there is a good chance you'll encounter someone you know or have met in the past. Although you might be tempted to pretend not (28) _____ or hear the other person if you are in a hurry, it's a good idea to be friendly and at least offer a greeting in return. Not doing so can label you a snob and that will stay with you for a long time.
When you see someone you know, it's a good form to start with a warm smile. If the situation allows, and you don't have your hands full of packages, extend your hand and offer a firm handshake, unless you have a cold. In that case, you can do a fist bump or explain that you might be (29) _____.

(25)........................

Read the following passage and mark the letter A, B, C, or D to indicate the correct word or phrase that best fits each of the numbered blanks. 
Do you ever find yourself flustered when you see someone you don't expect? Have you experienced those embarrassing and awkward moments (25) _____ you can't think of something to say? Prepare yourself for the future so you won't be caught off guard. Being prepared can (26) _____ the difference between feeling self-conscious and being confident as you express your delight (27) _____ seeing someone you know.
When you're out and about, there is a good chance you'll encounter someone you know or have met in the past. Although you might be tempted to pretend not (28) _____ or hear the other person if you are in a hurry, it's a good idea to be friendly and at least offer a greeting in return. Not doing so can label you a snob and that will stay with you for a long time.
When you see someone you know, it's a good form to start with a warm smile. If the situation allows, and you don't have your hands full of packages, extend your hand and offer a firm handshake, unless you have a cold. In that case, you can do a fist bump or explain that you might be (29) _____.

Read the following passage and mark the letter A, B, C, or D to indicate the correct word or phrase that best fits each of the numbered blanks. 
Sir Isaac Newton, the English scientist and mathematician, was one of the most important figures of the 17th century scientific revolution. One of his greatest achievement was the (25) _____ of the three laws of motion, which are still used today. But he also had a very unusual personality. Some people would say he was actually insane. 
His father died before he was born, and his mother soon remarried. The young Isaac hated his stepfather so much that he once (26) ____________ to burn his house down - when his stepfather and mother were still inside! Fortunately he did not, and he went on to graduate from Cambridge without being thrown into prison. 
Isaac's first published work was a theory of light and color. When another scientist wrote a paper criticizing this theory, Isaac flew into an uncontrollable rage. The scientist (27) _____________ for the criticism was a man called Robert Hooke. He was head of the Royal Society, and one of the most respected scientists in the country. (28)______________, this made no difference to Isaac, who refused to speak to him for over a year. 
The simple fact was that Isaac found it impossible to have a calm discussion with anyone. As soon as someone said something that he disagreed with, he would lose his (29) ____________. For this reason he lived a large part of his life isolated from other scientists. It is unlikely that many of them complained. 

(29).......................

Choose the underlined word or phrase (A, B, C or D) that is incorrect and needs to be changed: If my father hasn't encouraged me to take the exam, I wouldn't have done it

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions:
According to some accounts, the first optical telescope was accidentally invented in the 1600s by children who put two glass lenses together while playing with them in a Dutch optical shop. The owner of the shop, Hans Lippershey, looked through the lenses and was amazed by the way they made the nearby church look so much larger. Soon after that, he invented a device that he called a “looker”, a long thin tube where light passed in a straight line from the front lens to the viewing lens at the other end of the tube. In 1608 he tried to sell his invention unsuccessfully. In the same year, someone described the “looker” to the Italian scientists Galileo, who made his own version of the device. In 1610 Galileo used his version to make observations of the Moon, the planet Jupiter, and the Milky Way. In April of 1611, Galileo showed his device to guests at a banquet in his honor. One of guests suggested a name for the device: telescope
When Isaac Newton began using Galileo’s telescope more than a century later, he noticed a problem. The type of telescope that Galileo designed is called a refractor because the front lens bends, or refracts, the light. However, the curved front lens also caused the light to the separated into colors. This meant that when Newton looked through the refracting telescope, the images of bright objects appeared with a ring of colors around them. This sometimes interfered with viewing. He solved this problem by designing a new type of telescope that used a curved mirror. This mirror concentrated the light and reflected a beam of light to the eyepiece at the other end of the telescope. Because Newton used a mirror, his telescope was called a reflector
Very much larger optical telescopes can now be found in many parts of the world, built on hills and mountains far from city lights. The world’s largest refracting telescope is located at the Yerkes Observatory in Williams Bay, Wisconsin. Another telescope stands on Mount Palomar in California. This huge reflecting telescope was for many years the largest reflecting telescope in the world until an even larger reflecting telescope was built in the Caucasus Mountains. A fourth famous reflector telescope, the Keck Telescope situated on a mountain in Hawaii, does not use a single large mirror to collect the light. Instead, the Keck uses the combined light that falls on thirty- six mirrors
Radio telescopes, like optical telescopes allow astronomers to collect data from outer space, but they are different in important ways. First of all, they look very different because instead of light waves, they collect radio waves. Thus, in the place of lenses or mirror, radio telescopes employ bowl-shaped disks that resemble huge TV satellite dished. Also, apart from their distinctive appearance, radio telescope and optical telescopes use different methods to record the information they collect. Optical telescopes use cameras to take photographs of visible objects, while radio telescopes use radio receivers to record radio waves from distant object in space.

When was Galileo’s invention called “telescope”?

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 a small village in North Yorkshire, there is a big old farmhouse  (1) .......three families live    together. Alice and George and their three children, Joe and Pam and their two children, and Sue and her baby daughter. The adults divide up the work between them. George does the cooking, Joe and Sue do almost the housework. Pam looks after the shopping and (2)..... the repairs, and Alice takes care of the garden.
Alice, George and Sue go out to work. Joe works at home (3)...... computer systems, and Pam, who is a painter, looks after the baby during the day. Two of the children go to school in the village, but the three oldest ones go by bus to the secondary school in the nearest town, ten miles away.
The three families get (4)...... well, and enjoy their way of life. There are a few difficulties, of course. Their biggest worry at the moment is money- one of the cars needs replacing, and the roof needs some expensive repairs. But this isn't too serious- the bank has agreed to a loan, which they expect to be able to pay back in three years. And they all say they would much rather go on living in their old farmhouse (5)....... move to a luxury flat in a big city
(3)........................

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct answer to each of the questions:
Deforestation is the clearing, destroying, or otherwise removal of trees through  deliberate,  natural or accidental means. It can occur in any area densely populated by trees and other plant life, but the majority of it is currently happening in the Amazon rainforest. The loss of trees and other vegetation can cause climate change, desertification, soil erosion, fewer crops, flooding, increased greenhouse gases in the atmosphere, and a host of problems for indigenous people.
Deforestation occurs for a number of reasons, including: farming, mostly cattle due to its quick turn around; and logging for materials and development. It has been happening for thousands of years, arguably since man began converting from hunter/gatherer to agricultural based societies, and required larger, unobstructed tracks of land to accommodate cattle, crops, and housing. It was only after the onset of the modern era that it became an epidemic.
One of the most dangerous and unsettling effects of deforestation is the loss of animal and plant species due to their loss of habitat; not only do we lose those known to us, but also those unknown, potentially an even greater loss. Seventy percent of Earth's land animals and plants live in forests, and many cannot survive the deforestation that destroys their homes. The trees of the rainforest that provide shelter for some species also provide the canopy that regulates the temperature, a necessity for many others. Its removal through deforestation would allow a more drastic temperature variation from day to night, much like a desert, which could prove fatal for current inhabitants.
In addition to the loss of habitat, the lack of trees also allows a greater amount  of  greenhouse gases to be released into the atmosphere. Presently, the tropical rainforests of South America are responsible for 20% of Earth's oxygen and they are disappearing at a rate of 4 hectares a decade. If these rates are not stopped and reversed, the consequences will become even more severe.
The trees also help control the level of water in the atmosphere by helping to regulate the water cycle. With fewer trees left, due to deforestation, there is less water in the air to be returned to     the soil. In turn, this causes dryer soil and the inability to grow crops, an ironic twist when considered against the fact that 80% of deforestation comes from small-scale agriculture and cattle ranching.
Further effects of deforestation include soil erosion and coastal flooding, In addition to their previously mentioned roles, trees also function to retain water and topsoil, which provides the rich nutrients to sustain additional forest life. Without them, the soil erodes and washes  away,  causing farmers to move on and perpetuate the cycle. The barren land which is left behind in the wake of these unsustainable agricultural practices is then more susceptible to flooding, specifically in coastal regions. Coastal vegetation lessens the impact of waves and winds associated with a storm surge. Without this vegetation, coastal villages are susceptible to damaging floods.

The following are negative effects of deforestation, EXCEPT     .

Most of the people _________to the wedding banquet arrived late.

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct answer to each of the questions:
Education is another area of social life in which information technology is changing the way we communicate. Today's college students may not simply sit in a lecture or a library to  learn about their field. Through their computers and the wonders of virtual reality they can participate
in lifelike simulated experiences. Consider the following scenario of the future of education made possible through developments in information technology.
For children over the age of 10, daily attendance at schools is not compulsory. Some of the older children attend school only once or twice weekly to get tutorial support or instruction from a teacher. For the most part, pupils are encouraged to work online from home. Students must complete a minimum number of study hours per year; however, they may make up these hours by studying at home at times that suit their family schedule. They can log on early or late in the day and even join live classes in other countries. In order to ensure that each student is learning adequately, computer software will automatically monitor the number of hours a week each student studies online as well as that students' learning materials and assessment activities. Reports will be available for parents and teachers. The software can then identify the best learning activities and condition for each individual student and generate similar activities. It can also identify areas of weak achievement and produce special programs adjusted to the students' needs.

The word "they" in paragraph 2 refers to     .

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions:
Rachel Carson was bom in 1907 in Springsdale, Pennsylvania. She studied biology in college and zoology at Johns Hopkins University, where she received her master’s degree in 1933. In 1936, she was hired by the US Fish and Wildlife Service, where she worked most of her life.
Carson’s first book, Under the Sea Wind, was published in 1941. It received excellent reviews, but sales were poor until it was reissued in 1952. In that year, she published The Sea Around Us, which provided a fascinating look beneath the ocean’s surface, emphasizing human history as well as geology and marine biology. Her imagery and language had a poetic quality. Carson consulted no less than 1, 000 printed sources. She had voluminous correspondence and frequent discussions with experts in the field. However, she always realized the limitations of her non-technical readers.
In 1962, Carson published Silence Spring, a book that sparked considerable controversy. It proved how much harm was done by the uncontrolled, reckless use of insecticides. She detailed how they poison the food supply of animals, kill birds, and contaminate human food. At that time, spokesmen for the chemical industry mounted personal attacks against Carson and issued propaganda to indicate that her findings were flawed. However, her work was vindicated by a 1963 report of the President’s Science Advisory Committee.

The word “reckless” is closest in meaning to     .

Choose the underlined word or phrase (A, B, C or D) that is incorrect and needs to be changed: There are many another people who are members of the swim club

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct answer to each of the questions:
Recreational diving or sport diving is a type of diving that uses scuba equipment for the purpose of leisure and enjoyment. In some diving circles, the term "recreational diving" is used in contradistinction to "technical diving", a more demanding aspect of the sport  which  requires greater levels of training, experience and equipment.
Recreational scuba diving grew out of related activities such as snorkeling and underwater hunting. For a long time, recreational underwater excursions were limited by the  amount of  breath that could be held. However, the invention of the aqualung in 1943 by Jacques-Yves Cousteau and its development over subsequent years led to a revolution in recreational diving. However, for much of the 1950s and early1960s, recreational scuba diving was a  sport limited to  those who were able to afford or make their own kit, and prepared to undergo intensive training to use it. As the sport became more popular, manufacturers became aware of the potential market, and equipment began to appear that was easy to use, affordable and reliable. Continued advances in' SCUBA technology, such as buoyancy compensators, modern diving regulators, wet or dry suits,  and dive computers, increased the safety, comfort and convenience of the gear encouraging more people to train and use it.
Until the early 1950s, navies and other organizations performing professional diving were   the only providers of diver training, but only for their own personnel and only using their own    types of equipment. There were no training courses available to civilians who bought the  first  scuba equipment. Professional instruction started in 1959 when the non-profit National Association of Underwater Instructors was formed.
Further developments in technology have reduced the cost of training and diving. Scuba- diving has become a popular leisure activity, and many diving locations have some form of  dive  shop presence that can offer air fills, equipment and training. In tropical and sub-tropical parts of the world, there is a large market in holiday divers, who train and dive while on holiday, but rarely dive  close to home. Generally, recreational diving depths are limited to a maximum of between 30 and 40 meters (100 and 130 feet), beyond which a variety of safety issues make it unsafe to dive using recreation diving equipment and practices, and specialized training and equipment for technical diving are needed.

Recreational underwater excursions used to be limited    _.

Without the traffic jam on the high way this morning, I _________late for the meeting.