Whether one is awake or asleep, the brain emits electrical waves. These waves occur in predictable sleep cycles that can be measured with an electroencephalography, known more commonly as an EEG. During wakefulness, the waves are recorded at about ten small waves per second, but with the onset of sleep, the waves become larger and slower. The largest, slowest waves occur during the first three hours of sleep when mental activity slows down but does not stop. In fact, if awakened from slow waved sleep, a person can often remember vague thoughts that occurred during that period of sleep, but the sleeper does not generally dream. Referred to as NREM or non-REM sleep, it is characterized by large, slow waves. During sleep, intervals of small, fast waves also occur in patterns similar to those experienced while awake. The eyes move rapidly, and it appears to the observer that the sleeper is watching some event. Sleepers who are awakened during this rapid-eye-movement sleep will often recall the details of dreams they have been having. Sleep of this kind is called dreaming sleep or rapid-eye-movement sleep, also known REM sleep. REM sleep is emotionally charged. The heart beats irregularly, and blood pressure may be elevated. In contrast, the body is so still that the dreamer may appear to be paralyzed. In a period of eight hours, most sleepers experience from three to five instances of REM sleep. Each instance lasts from five to thirty minutes with an interval of at least ninety minutes between each one. Later instance of REM sleep are usually of longer duration than are instances earlier in the eight-hour period. Since people who suffer sleep deprivation experience fatigue, irritably, and loss concentration, we must conclude that sleep is essential because in some way it regenerates the brain and the nervous system. NREM sleep increases after physical exertion, whereas REM sleep tends to increase after a stressful day. Studies suggest that non-REM sleep may be especially helpful in restoring muscle control, whereas REM sleep may be more important in revitalizing mental activity. it appears that both kind of sleep are necessary, and the recuperation of sleep of one kind will not compensate for a lack of the other kind of sleep. (taken from BARRON'S Practice Exercises for The TOEFL 6th Edition, 2007) 20. It can be inferred from the passage that students who are writing term papers __ . A. require slow-wave sleep to increase mental activity B. can stay up all night working and recover the sleep they need by sleeping for a few hours the next afternoon C. need REM sleep to restore mental functioning D. do not need as much sleep because of the heightened brain waves involved in creative activity E. need to compensate their loss sleep during a stay up-night-study in the following nights

People who drink two or more sweetened soft drinks a week have much hig her risk of pancreatic cancer, an unusual but .... (42) ... . cancer. People who drink mostly fruit juice ... (43) .... sodas did not have the same risk. Sugar may be to .... (44).... but people who drink sweetened sodas regularly have other poor health habits. The high levels of sugar in soft drinks may be increasing the level of insulin in the body, which we think .... (45) .... to pancreatic cancer cell growth. Insulin which helps the body .... (46) .... sugar is made in the pancreas. 46. A. digest B. metabolize c. stimulate D. produce E. apply

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Since Mario is a presenter, he is used to .... in front of the spectators. A. Speak C. Speaking B. Speaks D. Spoke

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Since 1929, physicists have known that the universe is expanding. Most physicists hold that the entire observable universe was condensed into a tiny area of exceptional density and that this initial mass exploded outward in what is commonly referred to as the "Big Bang." The universe has been expanding steadily ever since this cataclysmic event and most physicists naturally assumed that this expansion must be gradually slowing down. Some theorists even predicted that the gravitational pull of the universe would cause the eventual contraction of the universe-the "Big Crunch." However, in 1998, a team of observers studying supernovae made a shocking discovery. Instead of slowing down, the expansion of the universe is accelerating. In fact, the acceleration appeared to have begun some 10 billion years ago. Later measurements of the cosmic microwave background and a survey of the distribution of galaxies seem to corroborate the initial finding that the expansion of the universe is indeed accelerating. Cosmologists believe the most likely explanation for the acceleration of the universe's expansion is an entity known as dark eriergy According to theory, dark energy should account for approximately twothirds of the total cosmic energy density. It also is believed to be gravitationally repulsive and diffused throughout the areas of space unoccupied y galaxies. Although theoretically possible, dark energy, if it were found to exist, would provide theorists with a number of difficulties and perhaps even require an extensive rethinking of fundamental physics. Some cosmologists believe that the existence of dark energy impl ies the existence of subatomic particles more than thirty orders of magnitude smaller than the electron. Others have tinkered with Einstein's theory of relativity in an attempt to account for the perceived effects of dark energy. Such drastic revisions to long-held tenets have encouraged some physicists to seek a more conventional solution to the accelerating universe enigma, one that does not invoke the specter of dark energy. These theories posit more mundane explanations, such as the aggregate gravitational effect of interstellar dust. Recently, four independent groups have found evidence of the integrated Sachs Wolfe effect, a phenomenon linked to the presence of dark energy. The passage is primarily concerned with .... A. defending an innovative theory B. comparing competing scientific theories C. detailing the ramifications of a finding D. describing a problem and its possible solution E. proposing a new approach to cosmology

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Forget lions, tigers, and bears. When it comes to the art of war, army ants are among the most frightening creatures on earth. With powerful mouth parts, these ighters can skillfully cut creatures much larger than themselves into pieces. Acting together in great number, army ant colonies succeed at making tens of thousands of such kills each day. Their capabilities do have limits, though. Contrary to popular belief, they almost never take down large animals or people. One of the best places to observe army ants is Barro Colorado, an island in a lake creates by Panama Canal. The island is home to as many as 50 colonies of Eciton burchellii, the most studied army ant in world. It is one of 150 types of army ants in the New World; more 170 other types live in Asia, Africa, and Australia. The colonies of this army ant are huge, ranging from 300.000 to 700.000 ants. They never stay in one place long, moving from nest site to nest site. Linking legs together, they use their own bodies to form enormous nests called bivouacs, which they hang beneath a fallen tree. There they stay for about 20 days as the queen lays as many as 300.00 eggs. When the ants go hunting as many as 200.000 of them leave the nest in a group that broadens into a fan as wide as 14 meters. This swarm raid takes a slightly diferent course each day, allowing the hunter to cover fresh ground each time. Protecting the ants wherever they go are soldiers, recognizable by their oversized jaws. If their frightening looks do not scare enemies away, soldier also have a powerful bite and the attack is often suicidal. Because their jaws are shaped like ishhooks, the soldiers cannot pull them out again. Amazonian tribes have used soldier ants to close wounds, breaking of the bodies and leaving the head in place. Eciton burchellii are blind and cannot see what a head of them is, but they move together in such great numbers that they can easily kill the non-army ants, insect and other small creatures that constitute their prey. When the groups happen upon a break in the path, ants immediately link legs together and form living bridges so that the groups can move forwards without any delay. In Japanese the word ant is written by linking two character: one meaning “insect”, the other meaning “loyalty”. Indeed, individual ants are completely loyal to their fellow ants. They display many examples of selless cooperation that, while certainly extreme, cannot fail to win human admiration. In which paragraphs of the text author mention the sight of army ants? A. 2 B. 3 C. 4 D. 5

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The author had died before his book __ . A. has been published B. had been published C. would be published D. was being published E. was published

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