单选题 All mammals require sleep; it is an essential part of life. For giraffes, two hours aLine day is enough. For bats, that number is closer to twenty. The average adult human needs between seven and nine hours of sleep every day. Despite these differences, mammals all have one thing in common: If they do not get enough sleep, they can(5) suffer serious mental and physical consequences. The most extensive sleep research has been conducted on people. Through these studies, scientists have identified two broad categories of sleep, which can be further divided into five stages with distinct physiological functions. Taken together, they form a complete sleep cycle. The first four stages are marked by a(30) lack of rapid eye movement (REM). Therefore, they are referred to as non-REM sleep. While people are engaged in non-REM sleep, several things are occurring. Researchers have discovered that during this early sleep, the human body releases a series of hormones responsible for the proper functioning of certain body systems. Disrupted sleep can cause these hormones to fall out of balance.(15) The results can contribute to disorders such as diabetes, depression, infertility, or even cancer. Lack of sleep, especially in stages 3 and 4, can literally stunt the growth of children and may increase rates of obesity in adults. Stage 5 sleep is defined by the occurrence of rapid eye movement, otherwise known as dreaming. Note that, while REM sleep is the final stage in a sleep cycle,(20) a complete cycle generally lasts only about 95 minutes. A person will experience four to six cycles in one sleep session, with REM sleep taking up a larger portion of the cycle as the night continues. Scientists have advanced several theories about why humans need REM sleep. One view is that dreaming aids in memory consolidation. Under this theory, during REM sleep the brain not only strengthens(25) memory of important actions or events, but it weakens memory of unimportant things. Another view is that dreaming is necessary for proper central nervous system development. Yet another theory suggests that REM sleep involves the repair of monoamine receptors. The theories are not necessarily exclusive; in fact, they all reach the conclusion that REM sleep deprivation can result in death.

单选题According to the passage, scientists have concluded which of the following from the discovery of the large amount of deuterium found in comets?(A) Comets do not contain enough deuterium to have solely created the Earth's oceans.(B) Given the ratio of deuterium to ordinary hydrogen in seawater, comets cannot have contributed to the Earth's oceans.(C) It is likely that comets contain less Xenon than meteorites do.(D) Given the low level of deuterium in the waters of Earth's oceans, comets cannot be its sole source.(E) Comets now play a greater role in the creation of the Earth's oceans than was previously thought.

单选题SPLENDOR:(A) foulness(B) corruption(C) avarice(D) transformation(E) sincerity

单选题It can be inferred from the passage that scientists are "perplexed by the means" (line 12) for which of the following reasons?

单选题The ______ of sediment in the river caused concern among environmentalists and industrialists alike; the water levels in the river were being reduced almost daily.(A) accretion(B) disposal(C) catalyst(D) alienation(E) ethnology

单选题RENEGADE : FEALTY ::(A) infidel: excommunication(B) apostate : euphoria(C) traitor: treason(D) bigot : tolerance(E) misanthrope : self-esteem

单选题COLLUSION: CONSPIRATORS ::(A) edition : journalists(B) collaboration : partners(C) sportsmanship : umpires(D) ascription : translators(E) summarization : critics

单选题Current estimates put thirteen percent of global flora at risk of extinction, but this number does not include ------- plants from tropical regions, where the majority of the world's plants grow.

单选题HERMITAGE : SECLUDED ::

单选题STUPOR: ALERT::

单选题According to the passage, scientists have decided that sulfur aerosols from volcanic eruptions affect global temperatures to a greater extent than ash clouds because(A) the greenhouse gas effect produced by human activities tends to have a much greater environmental effect than that of volcanic explosions(B) clouds of sulfur-rich gases tend to achieve greater heights in the stratosphere than do ash clouds(C) a particular explosion producing high sulfur and little ash had a greater environmental effect than the converse(D) the burning of fossil fuels tends to exacerbate the effects of sulfurous aerosols, but not those of ash clouds(E) global warming effects tend to minimize the impact of ash clouds, but not those of sulfurous aerosols

单选题According to the passage, which of the following statements about temperature gradients is true?

单选题Circular region C has a radius of 1 centimeter and a circumference of x centimeters: If the region has an area of y square centimeters, what is the ratio of x to y?

单选题TheilluminationE，infootcandles，providedbyalightsourceofintensityI，incandles，atadistanceD，infeet，iSgivenbyForanilluminationof50footcandlesatadistanceof4feetfromasource，theintensityofthesourcemustbeA.50candlesB.200candlesC.800candlesD.1，600candlesE.2，500candies

单选题It can be inferred from the examples given in the passage that medievalist backgrounds were problematic for Victorians for which of the following reasons?(A) They symbolized a reliance on irony that was typical not only of Pre-Raphaelite work but many other controversial movements.(B) They concealed an uncomfortable infatuation with the notion of sacrifice.(C) They avoided the sentimentality that was most revered and palatable at the time.(D) They indicated an affinity for pictorial modes of representation that ultimately contributed to Rossetti's popularity.(E) They presented a challenge to the average Victorian's reluctance to modernize and become nihilistic.

单选题The primary purpose of the passage is to(A) indicate some possible technological benefits to the development of new and varied techniques in nanotechnology(B) argue that science involving the macroscopic tends to be exponentially more difficult than the science of the microscopic(C) defend the use of the bottom-up approach of building molecules as more efficient relative to the top-down approach(D) distinguish two different approaches in nanotechnology and comment on their differences and similarities(E) correct the misconception that the benefits of nanotechnology are likely to be seen in the near future

单选题 x t u t a b u b c If y is a two—digit number with tens digit t and units digit M and the table above is a multiplication table for t and u (for example，t×u=6)，then y2= A. a+2b+10c B. 10a+20b+x C. 10(a+2b+c. D. 100(a+26+c. E. 100a+20b+c

单选题UAnalogies/U

单选题Rossetti's "appreciation of the world's physical beauty and its expression in lush images" is most probably alluded to by the author as an example of which of the following?(A) A sensibility that unites Rossetti to the rest of the Pre-Raphealites.(B) A sensibility that distinguish Rossetti as a more accomplished poet than her fellow Pre-Raphealites.(C) A suggestion of the reasons behind her choice to rely upon Christian imagery.(D) An aesthetic that was rather typical at the time for Victorian poets.(E) An aesthetic that suggests Rossetti may have had influences on poets peripheral to the Pre-Raphealite circle.