Read the following passage and choose the best answer (A, B, C, D):
The stylistic innovation in painting known as Impressionism began in the 1870s. The Impressionists wanted to depict what they saw in nature, but they were inspired to portray fragmentary moments by the increasingly fast pace of modern life. They concentrated on the play of light over objects, people, and nature, breaking up seemingly solid surfaces, stressing vivid contrast between colors in sunlight and shade, and depiction reflected light in all of its possibilities. Unlike earlier artists, they did not want to observe the world from indoors. They abandoned the studio, painting in the open air and recording spontaneous Impressions of their subjects instead of making outside sketches and then moving indoors to complete the work from memory. Some of the Impressionists' painting methods were affected by technological advances. For example, the shift from the studio to the open air was made possible in part by the advent of cheap rail travel, which permitted easy and quick access to the countryside or seashore, as well as by newly developed chemical dyes and oils that led to collapsible paint tubes, which enabled artists to finish their paintings on the spot. Impressionism acquired its name not from supporters but from angry art lovers who felt threatened by the new painting. The term "Impressionism" was born in 1874, when a group of artists who had been working together organized an exhibition of their paintings in order to draw public attention to their work. Reaction from the public and press was immediate, and derisive. Among the 165 paintings exhibited was one called Impression: Sunrise, by Claude Monet (1840- 1926), viewed through hostile eyes, Monet's painting of a rising sun over a misty, watery scene seemed messy, slapdash, and an affont to good taste. Borrowing Monet's title, art critics extended the term "Impressionism" to the entire exhibit. In response, Monet and his 29 fellow artists in the exhibit adopted the same name as a badge of their unity, despite individual differences. From then until 1886 Impressionism had all the zeal of a "church", as the painter Renoir put it. Monet was faithful to the Impressionist creed until his death, although many of the others moved on to new styles. 
4. The word "advent" in paragraph 2 is closest in meaning to: 

Choose the best anwers for the following questions.

The generation gap, which refers to a broad difference between one generation and another, especially between young people and their parents, usually leads to numerous conflicts. Such family conflicts can seriously threaten the relationship between parents and children at times.
 
It goes without saying that, however old their children are, parents still regard them as small kids and keep in mind that their offspring are too young to protect themselves cautiously or have wise choices. Therefore, they tend to make a great attempt to help their children to discover the outside world. Nevertheless, they forget that as children grow up, they want to be more independent and develop their own identity by creating their own opinions, thoughts, styles and values about life.

One common issue that drives conflicts is the clothes of teenagers. While teens are keen on wearing fashionable clothes which try to catch up with the youth trends, parents who value traditional clothes believe that those kinds of attire violate the rules and the norms of the society. It becomes worse when the expensive brand name clothes teens choose seem to be beyond the financial capacity of parents.

Another reason contributing to conflicts is the interest in choosing a career path or education between parents and teenagers. Young people are told that they have the world at their feet and that dazzling future opportunities are just waiting for them to seize. However, their parents try to impose their choices of university or career on them regardless of their children's preference.

Indeed, conflicts between parents and children are the everlasting family phenomena. It seems that the best way to solve the matter is open communication to create mutual trust and understanding.

The word “offspring” in the second paragraph refers to________.

Read the passage carefully, then choose the correct answers.

Having a best friend to confide in can bring a positive effect on our emotional health. An evening out with the closest friend may be the best guarantee of a good time. In fact, our best friend can prevent us from developing serious psychological problems such as depression and anxiety.

Best friendship evolves with time - we cannot go out and pick our best friend. We become friends with people who share common interests – at school or through hobbies, for example.

Best friends have usually known each other for years and stuck together through good and bad times. If you haven't got one, perhaps you are being too distant from people, or focusing too much on your work.

The word 'one' in the last paragraph refers to ________.

Choose the correct answer to complete the  following passage.

"In a healthy relationship, both partners respect, trust and embrace (1) ____ differences. Both partners are able to communicate (2) ____ their needs and listen to their partner, and work to resolve conflict in a rational and (3) ____ way. But maintaining a healthy relationship (4) ____ for skills many young people are never taught. A lack of these skills, and (5) ____ up in a society that sometimes celebrates violence or in a community that experiences a high (6) ____ of violence, can lead to unhealthy and even violent relationships among youth.

Dating violence (7) ____ psychological or emotional violence, such as controlling behaviours or jealousy; physical violence, such as hitting or punching. More than 20 per cent of all adolescents report having experienced (8) ____ psychological or physical violence from an intimate partner - and underreporting remains a concern.

Adolescents, (9) ____ older adolescents, often have romantic relationships, which are long-term, serious, and intimate. Society has a responsibility to provide young people with the resources, skills, and space (10) ____ to safeguard their physical and emotional well being in these relationships. Youth-serving professionals, educators, and parents can help young people in need access services to (11) ____ dating abuse victimisation. Research also has shown that programmes intended to prevent dating violence can be (12) ____."

4. But maintaining a healthy relationship (4) ____ for skills many young people are never taught.

Read the following passage and choose the best answer (A, B, C, D):
Fiberscopes are one of the most are one of the most important outcomes of he science of fiber optics. Fibers made of glass and transparent acrylic plastic are capable of conveying light energy, and when thousands of these fibers are combined in what is called a fiberscope, they can transmit images. The most common fiberscopes contain about 750,000 fibers, each 0.001 centimeter, or 10 microns, in diameter. For certain uses, the diameter of the fiber may be as small as 5 microns. Fiberscopes have a wide range of applications. In the medical field, physicians use fiberscopes to examine internal organs and as an aid in delicate surgeries. Miniature probes have also been developed to view muscle fiber, skin tissue, and blood cells. Fiberscopes have also found varied uses in industry, particularly to inspect or control operations in inaccessible areas. Bundles of fiberscopes fused together in a solid plate, called a faceplate, are being used in the manufacture of television tubes and other cathode- ray tube devices. The most far reaching applications of fiber-optic technology are in communication. Optical fibers carry voice messages for telephone service. The sound of the voice is electronically broken down into thousands of pulses per second, which causes a transmitting laser to send coordinated pulses of light through the optical fibers. At the receiving end, the light pulses are converted to electrical signals and the voice message is reconstructed. Light-wave communication systems can handle an immensely greater number of telephone calls and television programs than the current system, and they will form the basis of the “electronic superhighway” expected to crisscross the nation in the near future of the information age.
1. How do optical fibers carry voice message?

Read the passage carefully, then choose the correct answers.

Having a best friend to confide in can bring a positive effect on our emotional health. An evening out with the closest friend may be the best guarantee of a good time. In fact, our best friend can prevent us from developing serious psychological problems such as depression and anxiety.

Best friendship evolves with time - we cannot go out and pick our best friend. We become friends with people who share common interests – at school or through hobbies, for example.

Best friends have usually known each other for years and stuck together through good and bad times. If you haven't got one, perhaps you are being too distant from people, or focusing too much on your work.

According to the passage, ________.

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 from 19 to 23:

Holidays are rich in old traditions and are (19) _______in Scotland, Ireland, Wales and England. Christmas is a great English (20) _______ holiday, and in Scotland it is not kept at all, except by clerks in banks; all the shops, mills and factories are working. But six days later, (21)_______ New Year’s Eve, the Scots begin to enjoy themselves. People invite their friends to their house (22)_______ “sit the old year out and the new year in”. When the clock begins to strike, the head of the family (23)_______to the front door, opens it wide, and holds it until the last stroke. Then he shuts the door. He has let the old year out and the New Year in.

Question 22:..........................

Read the following passage and mark the letter A,B,C or D on your answer sheet to indicate the correct answer or phrase that best fits each of the numbered blanks from.

            Nowadays, teenagers have (18)______ more money and expensive possessions than their parents ever did. Articles like radios and bicycles, which cost a fortune (19) _____ decades ago, are now mass-produced and cheap. And items that nobody even dreamed of possessing twenty years ago, such as mobile phones and computers, are now in common places. Teenagers are definitely better off financially. However life is not easy for them. There is much more to worry about than there was in the past. Jobs are not as secure (20)_____ they used to be and teenagers can no (21) _____ be confident that the world will always be peaceful and free of pollution. 

            Teenagers drive their parents crazy (22)_____ many ways. Some of them spray their hair with amazing color, while others wear clothes that shock their parents. They all want (23)_____ own stereos, mobile phones and televisions. But these young people are not really behaving differently from how their parents behaved when they were young. Many today’s parents and grandparents will laugh when they (24)_____ crazy fashions they wore. Those adults, (25) _____ are parents now fought with their own parents about clothes and lifestyle. In fact, teenagers have fought with their parents (26)_____ time began and no doubt they will always.

(18)..............................................................

Read the following passage and choose the best answer (A, B, C, D):
The stylistic innovation in painting known as Impressionism began in the 1870s. The Impressionists wanted to depict what they saw in nature, but they were inspired to portray fragmentary moments by the increasingly fast pace of modern life. They concentrated on the play of light over objects, people, and nature, breaking up seemingly solid surfaces, stressing vivid contrast between colors in sunlight and shade, and depiction reflected light in all of its possibilities. Unlike earlier artists, they did not want to observe the world from indoors. They abandoned the studio, painting in the open air and recording spontaneous Impressions of their subjects instead of making outside sketches and then moving indoors to complete the work from memory. Some of the Impressionists' painting methods were affected by technological advances. For example, the shift from the studio to the open air was made possible in part by the advent of cheap rail travel, which permitted easy and quick access to the countryside or seashore, as well as by newly developed chemical dyes and oils that led to collapsible paint tubes, which enabled artists to finish their paintings on the spot. Impressionism acquired its name not from supporters but from angry art lovers who felt threatened by the new painting. The term "Impressionism" was born in 1874, when a group of artists who had been working together organized an exhibition of their paintings in order to draw public attention to their work. Reaction from the public and press was immediate, and derisive. Among the 165 paintings exhibited was one called Impression: Sunrise, by Claude Monet (1840- 1926), viewed through hostile eyes, Monet's painting of a rising sun over a misty, watery scene seemed messy, slapdash, and an affont to good taste. Borrowing Monet's title, art critics extended the term "Impressionism" to the entire exhibit. In response, Monet and his 29 fellow artists in the exhibit adopted the same name as a badge of their unity, despite individual differences. From then until 1886 Impressionism had all the zeal of a "church", as the painter Renoir put it. Monet was faithful to the Impressionist creed until his death, although many of the others moved on to new styles. 
8. The author mentions Renoir to give an example of an artist who: 

Choose the best anwers for the following questions.

The generation gap, which refers to a broad difference between one generation and another, especially between young people and their parents, usually leads to numerous conflicts. Such family conflicts can seriously threaten the relationship between parents and children at times.
 
It goes without saying that, however old their children are, parents still regard them as small kids and keep in mind that their offspring are too young to protect themselves cautiously or have wise choices. Therefore, they tend to make a great attempt to help their children to discover the outside world. Nevertheless, they forget that as children grow up, they want to be more independent and develop their own identity by creating their own opinions, thoughts, styles and values about life.

One common issue that drives conflicts is the clothes of teenagers. While teens are keen on wearing fashionable clothes which try to catch up with the youth trends, parents who value traditional clothes believe that those kinds of attire violate the rules and the norms of the society. It becomes worse when the expensive brand name clothes teens choose seem to be beyond the financial capacity of parents.

Another reason contributing to conflicts is the interest in choosing a career path or education between parents and teenagers. Young people are told that they have the world at their feet and that dazzling future opportunities are just waiting for them to seize. However, their parents try to impose their choices of university or career on them regardless of their children's preference.

Indeed, conflicts between parents and children are the everlasting family phenomena. It seems that the best way to solve the matter is open communication to create mutual trust and understanding.
 

Why do teenagers want to choose their university or career?

Read the following passage and choose the best answer (A, B, C, D):
If any of the inmates at Yancheng prison are considering an escape attempt, they’d better do it soon. The Chinese prison is currently wrapping up months of construction on a new “smart” surveillance system designed to monitor prisoners at every moment, including while they are in their cells. According an official, this will make prison breaks virtually impossible — but it might also wreak havoc on prisoners’ psyches. According to the South China Morning Post, the facility is almost finished installing a network of cameras and sensors capable of constantly tracking inmates. These cameras and sensors will feed into an AI system that uses facial identification and movement analysis technologies to monitor each individual inmate at the Chinese prison, producing a daily report about each one and flagging any unusual behavior. “For instance,” project representative Meng Qingbiao told SCMP, “if an inmate has been spotted pacing up and down in a room for some time, the machine may regard the phenomenon as suspicious and suggest close-up checks with a human guard.” This isn’t the first example we’ve seen of prison officials attempting to make facilities “smart”. In February, Hong Kong’s Correctional Services Department announced the implementation of several technologies designed to help prisoners stay safe during their imprisonment. However, Zhang Xuemin, a physiology professor at Beijing Normal University, told SCMP the new system will “definitely affect” the prisoners’ mental state. And while he didn’t elaborate on what that effect might be, past research has shown that constant surveillance can increase a person’s stress and anxiety levels, while decreasing their trust in others — meaning the trade off for an escape-proof “smart” prison might be the mental health of its inmates.
4. The word “this” in paragraph 2 refers to ......

"In American, although most men still do less housework than their wives, that gap has been halved since the 1960s. Today, 41 per cent of couples say they share childcare equally, compared with 25 percent in 1985. Men's greater involvement at home is good for their relationships with their spouses, and also good for their children. Hands-on fathers make better parents than men who let their wives do all the nurturing and childcare. They raise sons who are more expressive and daughters who are more likely to do well in school - especially in math and science.

In 1900, life expectancy in the United States was 47 years, and only four per cent of the population was 65 or older. Today, life expectancy is 76 years, and by 2025, it is estimated about 20 per cent of the U.S. population will be 65 or older. For the first time, a generation of adults must plan for the needs of both their parents and their children. Most Americans are responding with remarkable grace. One in four households gives the equivalent of a full day a week or more in unpaid care to an aging relative, and more than half say they expect to do so in the next 10 years. Older people are less likely to be impoverished or incapacitated by illness than in the past, and have more opportunity to develop a relationship with their grandchildren.

Even some of the choices that worry people the most are turning out to bemanageable. Divorce rates are likely to remain high, and in many cases marital breakdown causes serious problems for both adults and kids. Yet when parents minimize conflict, family bonds can be maintained. And many families are doing this. More non-custodial parents are staying in touch with their children. Child-support receipts are rising. A lower proportion of children from divorced families are exhibiting problems than in earlier decades. And stepfamilies are learning to maximize children's access to supportive adults rather than cutting them off from one side of the family."

1: Which of the following can be the most suitable heading for paragraph 1?

Read the following passage and choose the best answer (A, B, C, D):
Many of the most damaging and life-threatening types of weather-torrential rains, severe thunderstorms, and tornadoes-begin quickly, strike suddenly, and dissipate rapidly, devastating small regions while leaving neighboring areas untouched. One such event, a tornado, struck the northeastern section of Edmonton, Alberta, in July 1987. Total damages from the tornado exceeded $ 250 million, the highest ever for any Canadian storm. Conventional computer models of the atmosphere have limited value in predicting short-live local storms like the Edmonton tornado, because the available weather data are generally not detailed enough to allow computers to discern the subtle atmospheric changes that precede these storms. In most nations, for example, weather balloon observations are taken just once every twelve hours at locations typically separated by hundreds of miles. With such limited data, conventional forecasting models do a much better job predicting general weather conditions over large regions than they do forecasting specific local events. Until recently, the observation-intensive approach needed for accurate, very short-range forecasts, or "Nowcasts", was not feasible. The cost of equipping and operating many thousands of conventional weather stations was prohibitively high, and the difficulties involved in rapidly collecting and processing the raw weather data from such a network were insurmountable. Fortunately, scientific and technological advances have overcome most of these problems. Radar systems, automated weather instruments, and satellites are all capable of making detailed, nearly continuous observation over large regions at a relatively low cost. Communications satellites can transmit data around the world cheaply and instantaneously, and modern computers can quickly compile and analyzing this large volume of weather information. Meteorologists and computer scientists now work together to design computer programs and video equipment capable of transforming raw weather data into words, symbols, and vivid graphic displays that forecasters can interpret easily and quickly. As meteorologists have begun using these new technologies in weather forecasting offices, Nowcasting is becoming a reality.
1. What does the passage mainly discuss?

Read the text and choose the best option to fill in each blank numbered:
Keeping your distance
Personal space is a term that refers (1)_______  the distance we like to keep between ourselves and other people. When (2) _______ we do not know well gets too close we usually begin to feel uncomfortable. If a business colleague comes closer than 1.2 meters, the most common response is to move (3)______ Some interesting (4)______ have been done in libraries. If strangers come too close, many people get up and leave the building; others use different methods such as turning their back on the intruder. Living in cities has made people develop new skills for dealing with situations where they are very close to strangers. Most people on crowded trains try not to look at strangers; they avoid skin contact, and apologize if hands touch by mistake. People use newspapers (5)_______ a barrier between themselves and other people, and if they do not have one, they stare into the distance, making sure they are not looking into anyone’s eyes.

Read the following passage and choose the best answer (A, B, C, D):
The word "laser" was coined as an acronym for Light Amplifiation by the Stimulated Emission of Radiation. Ordinary light, from the Sun or a light bulb, is emitted spontaneously, when atoms or molecules get rid of excess energy by themselves, without any outside intervention. Stimulated emission is different because it occurs when an atom or molecule holding onto excess energy has been stimulated to emit it as light. Albert Einstein was the first to suggest the existence of stimulated emission in a paper published in 1917. However, for many years physicists thought that atoms and molecules always were much more likely to emit light spontaneously and that stimulated emission thus always would be much weaker. It was not until after the Second World War that physicists began trying to make stimulated emission dominate. They sought ways by which, one atom or molecule could stimulate many others to emit light, amplifying it to much higher powers. The first to succeed was Charles H. Townes, then at Colombia University in New York. Instead of working with light, however, he worked with microwaves, which have a much longer wavelength, and built a device he called a "maser", for Microwave Amplifiation by the Stimulated Emission of Radiation. Although he thought of the key idea in 1951, the first maser was not completed until a couple of years later. Before long, many other physicists were building masers and trying to discover how to produce stimulated emission even shorter wavelength. The key concepts emerged about 1957. Townes and Arthur Schawlow, then at Bell Telephone Laboratories, wrote it long paper outlining the conditions needed to amplify stimulated emission of visible light waves. At about the same time, similar ideas crystallized in the mind of Gordon Gould, then a 37-year-old graduate student at Columbia, who wrote them down in a series of notebooks. Townes and Schawlow published their ideas in a scientific journal, Physical Review Letters, but Gould filed a patent application. Three decades later, people still argue about who deserves the credit for the concept of the laser.
3: The word "it" in line 5 refers to .

Read the following passage and choose the best answer (A, B, C, D):
Butterflies are among the most extensively studied insects, an estimated 90 percent of the world's species have their scientific names. As a consequence, they are, perhaps, the best group of insects for examining patterns of terrestrial biotic diversity and distribution. Butterflies also have a favorable image with the general public. Hence, they are an excellent group for communicating information on science and conservation issues such as diversity. Perhaps the aspect of butterflies diversity that has received the most attention over the past century is the striking difference in species richness between tropical and temperate regions. For example, in 1875 one biologist pointed out the diversity of butterflies in the Amazon when he mentioned that about 700 species were found within an hour's walk, whereas the total number found on the British islands did not exceed 66, and the whole of Europe supported only 321. This early comparison of tropical and temperate butterflies' richness has been well confirmed. A general theory of diversity would have to predict not only this difference between temperate and tropical zones, but also patterns within each region, and how these patterns vary among different animal and plant groups. However, for butterflies, variation of species richness within temperate or tropical regions, rather than between them, is poorly understood. Indeed, comparisons of numbers of species among the Amazon basin, tropical Asia, and Africa are still mostly "personal communication" citations, even for vertebrates. In other words, unlike comparison between temperate and tropical areas, these patterns are still in the documentation phase. In documenting geographical variation in butterflies' diversity, some arbitrary, practical decisions are made. Diversity, number of species, and species richness are used synonymously; little is known about the evenness of butterfìy distribution. The New World butterflies make up the preponderance of examples because they are the most familiar species. It is hoped that by focusing on them, the errors generated by imperfect and incomplete taxonomy will be minimized
6. All of the followings are mentioned as being important parts of a general theory of diversity EXCEPT : 

Read the passage then choose the best answer to fill in each gap.

The human …….. (16) is only one small species in the living world. Many ……. (17) species exist on this planet. However, human beings have great influence on the rest of the world. ………..(18) are changing the environment by building cities and villages where forests once stood. They are …………(19) the water supply by using water for industry and agriculture. They are changing weather conditions by cutting down trees in the forests, and they are destroying the air by adding ……….. (20) to it.

16: .....................

By the mid-nineteenth century, the term "icebox" had entered the American language, but ice was still only beginning to affect the diet of ordinary citizens in the United States. The ice trade grew with the growth of cities. Ice was used in hotels, taverns, and hospitals, and by some forward-looking city dealers in fresh meat, fresh fish, and butter. After the Civil War (1860-1865), as ice was used to refrigerate freight cars, it also came into household use. Even before 1880, half the ice sold in New York, Philadelphia, and Baltimore, and one-third of that sold in Boston and Chicago, went to families for their own use. This had become possible because a new household convenience, the icebox, a precursor of the modern refrigerator, had been invented.
 Making an efficient icebox was not as easy as we might now suppose. In the early nineteenth century, the knowledge of the physics of heat, which was essential to a science of refrigeration, was rudimentary. The common-sense notion that the best icebox was one that prevented the ice from melting was of course mistaken, for it was the melting of the ice that performed the cooling. Nevertheless, early efforts to economize ice included wrapping the ice in blankets, which kept the ice from doing its job. Not until near the end of the nineteenth century did inventors achieve the nice balance of insulation and circulation needed for an efficient icebox.
 But as early as 1803, an ingenious Maryland farmer, Thomas Moore, had been on the right track. He owned a farm about twenty miles outside the city of Washington, for which the village of Georgetown was the market center. When he used an icebox of his own design to transport his butter to market, he found that customers would pass up the rapidly melting stuff in the tubs of his competitors to pay a premium price for his butter, still fresh and hard in neat, one-pound bricks. One advantage of his icebox, Moore explained, was that farmers would no longer have to travel to market at night in order to keep their produce cool.

The author describes Thomas Moore as having been "on the right track" to indicate that ______________.

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 from 24 to 28:

In Southeast Asia, many forests have been cut down to produce timber and to clear land for farms and industries. The destruction of forests has reduced the living space of wildlife. Much of Asia’s wildlife is also threatened by over-hunting. Many people kill animals for food or hunt them to sell to zoos, medical researchers, and pet traders. Because of habitat destruction and over-hunting, many large Asian animals, including elephants, rhinoceroses, and tigers, have become endangered.

In China, people have cut down most of the forests for wood, which has caused serious soil erosion. The soil is deposited in rivers and streams, which lowers the quality of the water. The Huang He, or Yellow River, is so named because the light-colored soil gives the water a yellowish color. The soil has also raised the river-bed. As a result, the Huang He often floods, causing great property damage and loss of life along its banks.

The Huang He often floods because _____.

Read the following passage and choose the best answer (A, B, C, D):
When jazz began to lose its reputation as "low-down" music and to gain well-deserved acclaim among intellectuals, musicians began to feature many instruments previously considered inappropriate for jazz. Whereas before the 1950s, jazz musicians played only eight basic instruments in strict tempo, in this decade they started to improvise on the flite, electric organ, piccolo, accordion, cello, and even bagpipes, with the rhythm section composed for strings or piano. Big bands no longer dominated jazz, and most changes emerged from small combos, such as the Dave Brubeck Quartet and the Gerry Mulligan Quartet. The Gerry Mulligan Quartet proved that a small, modern band could sound complete without a piano; the rhythm section consisted only of a set of drums and a string bass. Jazz continued to move in new directions during the 1960s. Saxophonist and composer Ornette Coleman led a quartet playing "free" jazz that was atonal. Pianist Cecil Taylor also conducted similar experiments with music, and John Coltrane included melodies from India in his compositions. In the 1970s musicians blended jazz and rock music into fusion jazz which combined the melodies and the improvisations of jazz with the rhythmic qualities of rock'n' roll, with three or five beats to the bar and in other meters. The form of jazz music was greatly affected by electric instruments and electronic implements to intensify, distort, or amplify their sounds. However, the younger musicians of the time felt compelled to include a steady, swinging rhythm which they saw as a permanent and essential element in great jazz.
7. The author of the passage implies that in the 1950s, jazz musicians

Read the following passage and choose the best answer (A, B, C, D):
Light from a living plant or animal is called bioluminescence, or cold light, to distinguish it from incandescence or heat-generating light. Life forms could not produce incandescent light without being burned. Their light is produced in chemicals combining in such a way that little or no measurable heat is produced, and the life forms generating it are unharmed. Although bioluminescence is a relatively complicated process, it can be reduced to simple terms. Living light occurs when luciferin and oxygen combine in the presence of luciferase. In a few cases, fireflies the most common, an additional compound called ATP is required. The earliest recorded experiments with bioluminescence in the late 1800s are attributed to Raphael Dubois, who extracted a luminous fluid from a clam, observing that it continued to glow in the test tube for several minutes. He named the substance luciferin, which means “the bearer of life”. In further research, Dubois discovered that several chemicals were required for bioluminescence to occur. In his notes, it was recorded that a second important substance, which he called luciferase, was always present. In later study of small, luminous sea creatures, Newton Harley concluded that luciferin was composed of carbon, hydrogen, and oxygen, which are the building blocks of all living cells. He also proved that there are a variety of luciferin and luciferase, specific to the plants and animals that produce them. Much remains unknown, but many scientists who are studying bioluminescence now believe that the origin of the phenomenon may be traced to a time when there was no oxygen in the Earth’s atmosphere. When oxygen was gradually introduced to the atmosphere, it was actually poisonous to life forms, plants and animals produced light to use up the oxygen in a gradual but necessary adaptation. It is speculated that millions of years ago, all life may have produced light to survive. As the millennia passed, life forms on Earth became tolerant of, and finally dependent on oxygen, and the adaptation that produced bioluminescence was no longer necessary, but some primitive plants and animals continued to use the light for new functions such as mating or attracting prey.
3. The word "primitive" in paragraph 3 is closest meaning to .