Read the following passage and choose the best answer (A, B, C, D):
The process of communication has so importance at present moment. It has great expansion and is a necessary agent of socialization. The social communication has great power in the human species, from the origin of the history. The media of social communication can be television, radio, cinema, written or audiovisual press and highways of the information. They do, generally, universalization of the culture of the people. They extend the horizons and the limits between countries. They promote new social models, conducts and values. And they promote a dominant ideology. Often, the media of social communication are very far from the reality of the individuals. They, generally, do not perceive the habitual context of the persons. The social media complement and collaborate in the process of socialization of the new generations, from a positive opinion. Advertising and commercial messaging, pose consumerist models, from a negative perspective. The mass media convert a genuine culture into a consumer society. The advertising stimulates the need to consume, desperately. It transforms the persons into consumers of products. The advertising has a great power on the persons and it transports a serious addiction. The family, the educational system and the society, must allow the process of socialization and formation, to all people. They also must give the tools of analysis and the critique. They also must give offers of interesting things. They must promote the respect to the desires and different opinions. They also must promote the capacity of choice. The mass media influence the children and young people. They have models of identification, values, guidelines and policies. Often, they do not coincide with the own reality. They can serve to think. The mass media influence the process of social adjustment  
5. What is the overall tone of the paragraph 4?

Choose the best answer:
The teacher said Columbus ............... America in 1942.

Read the following passage and choose the best answer (A, B, C, D):
The Sahara Desert is the world’s largest hot desert. The Sahara is in North Africa and is as large as the United States. Many people think that an area like this has no animals or plant life, but they are (1) __________. In fact, the Sahara Desert has many different ‘ecoregions’. Each ecoregion has different plants and animals (2)_________there. The biggest ecoregion is called the ‘Sahara Desert ecoregion.’ In this area, the climate is extremely dry and extremely hot. The landscape is sandy and dusty with many high dunes. Because the Sahara Desert ecoregion is so hot and dry, there are very few plants and animals. Scientists estimate that there are only 500 species of plants. This is not very much when thinking of (3)_________ enormous the region is. These plants include acacia trees, palms, spiny shrubs, and grasses. The Sahara is also home to 70 species of mammals. Twenty of these are large mammals. There are about 90 species of birds and around 100 reptiles. The biggest threat to plants and animals in this environment is drying (4)_______. Because of this, plants have the ability to recover their health after their leaves have dried out completely. Animals can lose 30-60% of their body mass and still survive. Most animals do not get their water from drinking like other ecosystems. Instead, they have adapted to get their water through metabolic processes. This is why they can survive in a place (5)______ the Sahara Desert ecosystem

Rewrite the sentence:
Did you fly to Los Angeles?

Read the following passage and choose the best answer (A, B, C, D):
Australia has a well-organized and well-structured education system. The education starts at the age of five or six, but it may differ by a narrow margin between states. It starts with the preschool education which is not compulsory and can be offered within a school or separately. The primary and secondary school encompasses the compulsory education for Australians. There are a large number of primary and high school across the country with most of them being public schools. It is estimated that public schools amount to 60% of scholars as opposed to 40% in private settings. All these education providers must be licensed by the government and must fulfill certain requirements including infrastructure and teaching. Universities, on the other hand, are mainly public institutions. The Australian education system has established a standard curriculum so all scholars will be given the same quality of education. Despite there may be some states at which this curriculum is modified a bit, but the change is not that significant. The actual curriculum set  out in Australia education system is based on important abilities one must have in his life: Literacy, Numeracy, Information and communication technology, Critical and creative thinking, personal and social capability, ethical understanding, intercultural understanding. Vocational and Technical schools prepare students that want to skip the university and want to move directly to the job market. Actually, here it stands the difference between universities and colleges: the Vocational and Technical Schools are more oriented in teaching practical skills while university courses are mainly theory-based to lead students to different academic careers. There are hundreds of other schools out there that provide technical and further education (TAFE) and vocational education and training (VET). These schools offer short courses, certificates I through IV, diplomas, and advanced diplomas. They focus on training their students in a particular vocation or just to help their students get out into the workplace. These schools offer a wide variety of courses and qualifications attained by these courses can lead to different career pathways to follow afterward  Australian higher education modernity and reputation relies on a huge number of educational providers including universities and different training organizations. Currently, there are 43 universities across the country. The vast majority of universities are public except two private universities. The world-class teaching offered is surely undisputed. Seven Australian universities are traditionally found at the top 100 best universities in the world which is a sufficient indicator to highlight their quality. Besides universities, more than 5,000 training organizations are registered and accredited. Actual figures show that the number of enrolled students is around 3.8 million with international students sharing more than half a million. There are also 3 self-accrediting higher education institutions. Furthermore, dozens of smaller schools do not grant any degrees or have an accreditation – these are private schools that focus on theology, business, information technology, natural therapies, hospitality, health, law, and accounting.  
7. The word “undisputed” in paragraph 4 could be best replaced by ________

Read the following passage and choose the best answer (A, B, C, D):
Parents in most cases want the best for their children, and to ensure this, they are  pushed to actively engage in their children’s lives, to ensure that they are making the right choices. Some parents, however, go to the extent of wanting to have the upper hand even when it comes to taking major decisions, such as choosing a career.  Local comedian and actor, Michael Sengazi, was obliged by his parents to pursue a career in law, a path he followed when he joined University of Kigali, but deep down he knew this wasn’t his dream career. This is why after graduating he chose to follow his passion —comedy. His parents failed to understand how a qualified lawyer could decide to go for comedy because they didn’t see it as a ‘well-paying job’. He had a challenge of convincing them to bless his journey. “So, I asked them to give me one year to try and see if comedy would work out for me. I worked hard and my parents realised that I could achieve big things, and they gave me the freedom to pursue the career.”  Bienvenue Muragwa, a career consultant at The Southern New Hampshire University based in Rwanda, says that parents are only allowed to guide the child during the career guidance process, but not take the final decision. “Parents are not allowed to choose or take the final decision for their children as the performance of the student is the assessing parameter of the career to be pursued,” he explains.  Shalom Azabe, a graduate in general counselling at Kampala Christian University, says in most African countries, not only Rwanda, children are overly dependent on their parents, yet this shouldn’t be the case. She recommends picking a leaf from westerners who endeavour to learn their children’s interests, something she says aides them in career guidance for the child. “Normally, a child starts to demonstrate a choice in career at 14 years of age. This is when parents need to sit down and make analysis that would help them guide their child in choosing the fitting option to undertake. This is in fact considered as overprotection as parents want to exercise their authority on their kids unwillingly, yet this affects them psychologically, and when the kid later on fails, they encounter a regret of pursuing studies that were not their choice in the first place,” Azabe said.
8. Which of the following can be inferred from the passage?

Choose the best answer:
Hue was listed as a world cultural Heritage by UNESCO ___________ 1993.

Read the following passage and choose the best answer (A, B, C, D):
Practical experience is a must-have for today’s job seekers. According to Brazen Life’s Huffington Post article titled “Why Gaining Work Experience Is More Important Than Your Education,” many colleges and universities report that students who have completed an internship or gained work experience during their studies have higher rates of getting hired. For example, at Iowa State University, of all students who completed a co-op program to earn a BS in engineering, an astounding 90 percent got jobs after graduation. Why is practical experience so important? There are a number of reasons why you need practical work experience. First, it’s simply the smart thing to do when you’re preparing for a career in a specific field. Let’s say it’s your dream to work as a consultant for an international corporate relocation company because you love international travel and you like organizing things. So you get a part-time job working as an office assistant at a corporate relocation company… and you find out it’s very different from what you expected. In short, you realize this isn’t the job for you-and you can concentrate on finding another job where you can put your passion and skills to work, for example in the tourism industry. Alternatively, you might find out that you enjoy the corporate relocation business. That means you’re gaining invaluable industry experience that will look great on your resumé when you apply for a full-time job.  Second, practical work experience teaches valuable soft skills, such as discipline, perseverance, teamwork, leadership skills, communication skills and problem solving. Employers will look for these in candidates and they’ll want to see proof. If you’ve spent a month as a team leader at Homes for Heroes, the leadership skills, teamwork experience and problem-solving abilities you developed there can add significant value to your candidacy. Third, working helps you build your network and can provide you with contacts in your chosen field. These contacts can be extremely useful when it comes to hearing about job leads and interesting opportunities. In addition, if you’ve impressed someone, he or she might be willing to write you a letter of recommendation for a job or a place in a graduate program.  Finally, the company you’re working for might offer you a position after you’ve graduated. Your employer already knows your skills and abilities, and you’re already acquainted with the company-so it’s a win-win situation! 
4. The word “they” in paragraph 3 refers to _____

Read the following passage and choose the best answer (A, B, C, D):
Many adults in America and increasing numbers elsewhere take part in mentoring schemes. A mentor is an adult who provides support and friendship to a young person. There are numerous different (1)_____ of mentoring: passing on skills, sharing experiences, offering guidance. Sometimes the most helpful thing to do is just listen. Mentoring is open to anybody - no particular (2) _____ experience is required, just a desire to make a difference to the life of a young person who needs help. This may seem a difficult thing at first, but many people find they have a real talent for it.  The support of a mentor can play an important part in a child’s development and can often make up (3) _____ a lack of guidance in a young person’s life. It can also improve young people’s attitudes towards society and build up their confidence in dealing with life’s challenges. For the mentor, it can be incredibly rewarding to know that they have had a significant influence on a child and helped to give the best possible (4) _____ in life. Indeed, it is not only adults who are capable of taking on this role. There is now an increasing (5) _____ for teenagers to mentor young children, for example by helping them with reading or other school work

Read the following passage and choose the best answer (A, B, C, D):
There are three main periods in Beethoven’s music career: early, middle and late. The beginning of his early period was in 1792 when he moved to Vienna, Austria. Beethoven quickly (1) ________ a name for himself as a talented pianist. His compositions during this period consisted mainly of works for his main instrument, the piano, and were classical in nature. (2)___________, Beethoven’s hearing was beginning to deteriorate during this period, and he tried to hide this fact from those around him. In 1800, Beethoven turned from the classical forms of the previous century to a more expressive or romantic music. His musical imagination began to grow (3)______ that of the piano. The middle period was believed to be Beethoven’s greatest and most productive stage. In less than a decade, he produced countless masterpieces in every genre. In 1809, however, his musical (4)_________ began to decline, possibly due to his health problems and mental state. Beethoven stopped conducting and performing in public, but continued to compose – many of his most admired works were created during this period. By 1815, he was almost completely deaf and his manners became increasingly rude. In 1827, he died after a long illness. Nearly 20,000 people lined the streets of Vienna to (5)_________ their last respect to the composer who had changed the music scene of Western Europe 

Choose the best answer:
A class began seven years ___________ with a mix of children who are dumb, deaf and mentally retarded.

Read the following passage and choose the best answer (A, B, C, D):
In 1959 Xerox created the first plain paper copy machine. It was one of the most  successful products ever. The company name Xerox grew into a verb that means “to copy,” as in “Bob, can you Xerox this for me?” Around 50 years later, the same thing happened to Google. Their company name grew into a verb that means “to do an internet search.” Now everyone and their grandma knows what it means to Google it.  Unlike Xerox, Google wasn’t the first company to invent their product, not by a long shot. Lycos released their search engine in 1993. Yahoo! came out in 1994. AltaVista began serving results in 1995. Google did not come out until years later, in 1998. Though a few years difference may not seem like much, this is a major head start in the fast moving world of tech. So how did Google do it? How did they overtake their competitors who had such huge leads in time and money? Maybe one good idea made all the difference.  There are millions and millions of sites on the internet. How does a search engine know which ones are relevant to your search? This is a question that great minds have been working on for decades. To understand how Google changed the game, you need to know how search engines worked in 1998. Back then most websites looked at the words in your query. They counted how many times those words appeared on each page. Then they might return pages where the words in your query appeared the most. This system did not work well and people often had to click through pages and pages of results to find what they wanted.  Google was the first search engine that began considering links. Links are those blue underlined words that take you to other pages when you click on them. Larry Page, cofounder of Google, believed that meaningful data could be drawn from how those links connect. Page figured that websites with many links pointing at them were more important than those that had few. He was right. Google’s search results were much better than their rivals. They would soon become the world’s most used search engine.  It wasn’t just the great search results that led to Google becoming so wellliked. It also had to do with the way that they presented their product. Most of the other search engines were cluttered. Their home pages were filled with everything from news stories to stock quotes. But Google’s homepage was, and still is, clean. There’s nothing on it but the logo, the search box, and a few links. It almost appears empty. In fact, when they were first testing it, users would wait at the home page and not do anything. When asked why, they said that they were, “waiting for the rest of the page to load.” People couldn’t imagine such a clean and open page as being complete. But the fresh design grew on people once they got used to it. 
7. Which was cited as a reason why Google became so popular?

Read the following passage and choose the best answer (A, B, C, D):
For 150 years scientists have tried to determine the solar constant, the amount of solar energy that reaches the Earth. Yet, even in the most cloud-free regions of the planet, the solar constant cannot be measured precisely. Gas molecules and dust particles in the atmosphere absorb and scatter sunlight and prevent some wavelengths of the light from ever reaching the ground. With the advent of satellites, however, scientists have finally been able to measure the Sun's output without being impeded by the Earth's atmosphere. Solar Max, a satellite from the National Aeronautics and Space Administration (NASA), has been measuring the Sun's output since February 1980. Although a malfunction in the satellite's control system limited its observation for a few years, the satellite was repaired in orbit by astronauts from the space shuttle in 1984. Max's observations indicate that the solar constant is not really constant after all. The satellite's instruments have detected frequent, small variations in the Sun's energy output, generally amounting to no more than 0.05 percent of the Sun's mean energy output and lasting from a few weeks. Scientists believe these fluctuations coincide with the appearance and disappearance of large groups of sunspots on the Sun's disk. Sunspots are relatively dark regions on the Sun's surface that have strong magnetic fields and a temperature about 2,000 degrees Fahrenheit cooler than the rest of the Sun's surface. Particularly large fluctuations in the solar constant have coincided with sightings of large sunspot group. In 1980, for example, Solar Max's instrument, registered a 0.3percent drop in the solar energy reaching the Earth. At that time a sunspot group covered about 0.6 percent of the solar disk, an area 20 times larger than the Earth's surface. Long-term variations in the solar constant are more difficult to determine. Although Solar Max's data have indicated a slow and steady decline in the Sun's output, some scientists have thought that the satellite's aging detectors might have become less sensitive over the years, thus falsely indicating a drop in the solar constant. This possibility was dismissed, however, by comparing Solar Max's observations with data from a similar instrument operating on NASA's Nimbus 7 weather satellite since 1978.
1. What does the passage mainly discuss?

Mark the letter A, B, C, or D on your answer sheet to indicate the undelined part that needs correction in each of the following questions:
In the course of its history, human inventions have dramatically increased the average amount of energy available for use per person. Primitive peoples in cold regions burned wood and animal dung to heat their caves, cook food, and drive off animals by fire. The first step toward the developing of more efficient fuels was taken when people discovered that they could use vegetable oils and animal fats in lieu of gathered or cut wood. Charcoal gave off more intensive heat than wood and was more easily obtainable than organic fats. The Greeks first began to use coal for metal smelting in the 4th century, but it did not come into extensive use until the Industrial Revolution.
In the 1700s, at the beginning of the Industrial Revolution, most energy used in the United States and other nations undergoing industrialization was obtained from perpetual and renewable sources, such as wood, water streams, domesticated animal labor, and wind. These were predominantly locally available supplies. By mid-1800s, 91 percent of all commercial energy consumed in the United States and European countries was obtained from wood. However, at he beginning of the 20th century, coal became a major energy source and replaced wood in industrializing countries. Although in most regions and climate zones wood was more readily accessible than coal, the latter represents a more concentrated source of energy. In 1910, natural gas and oil firmly replaced coal as the main source of fuel because they are lighter and, therefore, cheaper to transport. They burned more cleanly than coal and polluted less. Unlike coal, oil could be refined to manufacture liquid fuels for vehicles, a very important consideration in the early 1900s, when the automobile arrived on the scene.
By 1984, non-renewable fossil fuels, such as oil, coal, and natural gas, provided over 82 percent of the commercial and industrial energy used in the world. Small amounts of energy were derived from nuclear fission, and the remaining 16 percent came from burning direct perpetual and renewable fuels, such as biomass. Between 1700 and 1986, a large number of countries shifted from the use of energy from local sources to a centralized generation of hydropower and solar energy converted to electricity. The energy derived from non-renewable fossil fuels has been increasingly produced in one location and transported to another, as is the case with most automobile fuels. In countries with private, rather than public transportation, the age of non-renewable fuels has created a dependency on a finite resource that will have to be replaced.
Alternative fuel sources are numerous, and shale oil and hydrocarbons are just two examples. The extraction of shale oil from large deposits in Asian and European regions has proven to be labor consuming and costly. The resulting product is sulfur-and nitrogen-rich, and large scale extractions are presently prohibitive. Similarly, the extraction of hydrocarbons from tar sands in Alberta and Utah is complex. Semi-solid hydrocarbons cannot be easily separated from the sandstone and limestone that carry them, and modern technology is not sufficiently versatile for a large-scale removal of the material. However, both sources of fuel may eventually be needed as petroleum prices continue to rise and limitations in fossil fuel availability make alternative deposits more attractive.

What is the main topic of the passage?

Read the following passage and choose the best answer (A, B, C, D):
Next time your boss asks you to work late and miss your band rehearsal or board game night, point them to a new study in the Journal of Vocational Behavior. Researchers have found that spending more time on a hobby can boost people’s confidence in their ability to perform their job well. Ciara Kelly at Sheffield University and colleagues recruited 129 hobbyists — from amateur climbers to improv comedians — to look at how the time spent on their hobbies shaped their work life. To begin with, the team measured the seriousness of each participant’s hobby, asking them to rate their agreement with statements like “I regularly train for this activity”, and also assessed how similar the demands of their job and hobby were. Then, each month for seven months, participants recorded how many hours they had dedicated to their activity, and completed a scale measuring their belief in their ability to effectively do their job, or their “self-efficacy”, in which they rated themselves on statements like “At work I am able to successfully overcome many challenges”.  The researchers found that when participants spent longer than normal doing their leisure activity, their belief in their ability to perform their job increased. But this was only the case when they had a serious hobby that was dissimilar to their job, or when their hobby was similar to their work but they only did it casually. When their hobby was both serious and similar to their job, then spending more time on it actually had a detrimental effect, decreasing their self-efficacy. Why might that be? To maintain a serious hobby, people need to invest significant psychological resources, so if the activity has the same kinds of demands as their work, they may be left drained and unable to perform as well at their job. But if their hobby is quite different from their career, it may not interfere in the same way but instead help them develop other knowledge and skills that can boost their confidence at work. Of course, the data don’t provide conclusive evidence about the direction of the effect. Still, the results suggest that companies may want to encourage employees to pursue interests outside of work, as long as those activities differ from their day-to-day tasks. And they also may give pause to those who dream of packing it all in and turning their hobby into a career.  
5. According to paragraph 3, what do the results suggest from the subjects’ behaviours?

Read the following passage and choose the best answer (A, B, C, D):
Advertising helps people recognize a particular brand, persuades them to try it, and tries to keep them loyal to it. Brand loyalty is perhaps the most important goal of consumer advertising. Whether they produce cars, canned foods or cosmetics, manufacturers want their customers to make repeated purchases. [2] The quality of the product will encourage this, of course, but so, too, will affect advertising. Advertising relies on the techniques of market research to identify potential users of a product. [3] Are they homemakers or professional people? Are they young or old? Are they city dwellers or country dwellers? Such questions have a bearing on where and when ads should be placed. By studying readership breakdowns for newspapers and magazines as well as television ratings and other statistics, an advertising agency can decide on the best way of reaching potential buyers. Detailed research and marketing expertise are essential today when advertising budgets can run into thousands of millions of dollars. [4] Advertising is a fast-paced, high-pressure industry. There is a constant need for creative ideas that will establish a personality for a product in the public’s mind. Current developments in advertising increase the need for talented workers. In the past, the majority of advertising was aimed at the traditional white family - breadwinner father, non-working mother, and two children. Research now reveals that only about 6 percent of American households fit this stereotype. Instead, society is fragmented into many groups, with working mothers, single people and older people on the rise. To be most successful, advertising must identify a particular segment and aim its message toward that group. Advertising is also making use of new technologies. Computer graphics are used to grab the attention of consumers and to help them see products in a new light. The use of computer graphics in a commercial for canned goods, for instance, gave a new image to the tin can  
1. What does the passage mainly discuss?

Read the following passage and choose the best answer (A, B, C, D):
Just as optical fibers have transformed communication, they are also revolutionizing medicine. These ultra - thin, flxible fiers have opened a window into the living tissues of the body. By inserting optical fibers through natural openings or small incisions and the threading them along the body's established pathways, physicians can look into the lungs, intestines, heart and other areas that were formerly inaccessible to them. The basic fiber-optics system is called fiberscope, which consists of two bundles of fibers. One, the illuminating bundle, carries light to the tissues. It is coupled to a high-intensity light source. Light enters the cores of the high-purity silicon glass and travels along the fibers. A lens at the end of the bundle collects the light and focuses it into the other bundle, the imaging bundle. Each fibers in the bundle transmits only a tiny fraction of the total image. The reconstructed image can be viewed through an eyepiece or displayed on a television screen. During the last five years, improved methods of fabricating optical fibers have led to a reduction in fiberscope diameter and an increase in the number of fibers, which in turn has increased resolution. Optical fibers can also be used to deliver laser light. By use of laser beams, physicians can perform surgery inside the body, sometimes eliminating the need of invasive procedures in which healthy tissue must be cut through to reach the site of disease. Many of these procedures do not require anesthesia and can be performed in a physician's office. These techniques have reduced the risk and the cost of medical care.
1. What is the main topic of the passage?

Read the following passage and choose the best answer (A, B, C, D):
In the folklore of the Navajo people, it was said that frogs and toads fell from the sky when it (1)________. The phenomenon that gave rise to this belief involved the spade foot toad, which remains dormant beneath the Sonoran Desert of Arizona, (2)_________ the heat and drought for as long as eight or nine months. With the onset of summer thunderstorms, however, the toads respond to the vibrations of drumming raindrops and emerge, as if fallen from the sky with the rain, (3)__________their brief and frantic mating season. The male spade foot sits in a muddy pool and fills the night with his calls, attempting to attract a female of the same species. Once a female joins him, she may lay as many as 1,000 eggs in the small pool of rainwater. From that point it’s a race against the elements for the young, (4)_________ must hatch and mature with remarkable speed before the pool evaporates beneath the searing desert sun. As the pool grows smaller and smaller, it became thick with tadpoles fighting for survival in the mud, threatened not only by the loss of their watery nest but also by devouring insects and animals. In as few as nine days after fertilization of the eggs, those lucky enough to survive develop through each tadpole stage and finally emerge as fully formed toads. After (5)______ themselves on insects, the young toads like their parents, burrow underground, where they will lie dormant awaiting the next summer’s storms

Each sentence has a mistake. Findit by chosing A B C or D

In ancient Greek traditional, weapons and stable gear were placed upon the grave

Read the following passage and choose the best answer (A, B, C, D):
A scientist said robots will be more (1) ____ than humans by 2029. The scientist’s  name is Ray Kurzweil. He works for Google as Director of Engineering. He is one of the world’s leading experts on artificial intelligence (A.I.). Mr Kurzweil believes computers will be able to learn from experiences, just like humans. He also thinks they will be able to (2) ____ jokes and stories, and even flirt. Kurzweil’s 2029 prediction is a lot sooner than many people thought. The scientist said that in 1999, many A.I. experts said it would be hundreds of years before a computer was more intelligent than a human. He said that it would not be (3) ____ before computer intelligence is one billion times more powerful than the human brain.  Mr Kurzweil joked that many years ago, people thought he was a little crazy for predicting computers would be as intelligent as humans. His thinking has stayed the same but everyone else has changed the way they think. He said: “My views are not radical any more. I’ve actually stayed consistent. It’s the rest of the world that’s changing its view.” He highlighted examples of (4) ____ -tech things we use, see or read about every day. These things make us believe that computers have intelligence. He said people think (5) ____ now: “Because the public has seen things like Siri (the iPhone’s voice recognition technology) where you talk to a computer, they’ve seen the Google self-driving cars.”

Mark the letter A, B, C, or D on your answer sheet to indicate the undelined part that needs correction in each of the following questions:
Under certain circumstances, the human body must cope with gases at greater-than-normal atmospheric pressure. For example, gas pressures increase rapidly during a drive made with scuba gear because the breathing equipment allows divers to stay underwater longer and dive deeper. The pressure exerted on the human body increases by 1 atmosphere for every 10 meters of depth in seawater, so that at 39 meters in seawater a diver is exposed to pressure of about 4 atmospheres. The pressure of the gases being breathed must equal the external pressure applied to the body,

otherwise breathing is very difficult. Therefore all of the gases in the air breathed by a scuba diver at 40 meter are present at five times their usual pressure. Nitrogen, which composes 80 percent of the air we breathe, usually causes a balmy feeling of well-being at this pressure. At a depth of 5 atmospheres, nitrogen causes symptoms resembling alcohol intoxication, known as nitrogen narcosis. Nitrogen narcosis apparently results from a direct effect on the brain of the large amounts of nitrogen dissolved in the blood. Deep dives are less dangerous if helium is substituted for nitrogen, because under these pressures helium does not exert a similar narcotic effect.
As a scuba diver descends, the pressure of nitrogen on the lungs increases. Nitrogen then diffuses from the lungs to the blood, and from the blood to body tissues. Nitrogen then diffuses from the lungs to the blood, and from the blood to body tissues The reverse occurs when the diver surfaces, the nitrogen pressure in the lungs falls and the nitrogen diffuses from the tissues into the blood, and from the blood into the lungs. If the return to the surface is too rapid, nitrogen in the tissues and blood cannot diffuse out rapidly enough and nitrogen bubbles are formed. They can cause severe pains, particularly around the joints.
Another complication may result if the breath is held during ascent. During ascent from a depth of 10 meters, the volume of air in the lungs will double because the air pressure at the surface is only half of what it was at 10 meters. This change in volume may cause the lungs to distend and even rupture. This condition is called air embolism.
To avoid this event, a diver must ascend slowly, never at a rate exceeding the rise of the exhaled air bubbles, and must exhale during ascent.

What does the passage mainly discuss?