托福-练习十三及答案解析.doc

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1、托福-练习十三及答案解析(总分：39.00，做题时间：90 分钟)一、Passage 1(总题数：1，分数：13.00)Transient Lunar PhenomenaFor many years, sky watchers have reported seeing mysterious sights known as Transient Lunar Phenomena (TLP) on the surface of the moon. These are of two main types: fleeting flashes of light and spreading clouds of

2、 mist. Most professional astronomers have tended to dismiss these phenomena as figments of the observers imagination or as “observational errors“: either optical illusions or problems with the observers telescopes. One explanation put forth by professional astronomers blames the flashes on Earth sat

3、ellites passing in front of the moon. Satellite surfaces can flash like a cars windshield in sunlight, simulating a lunar flash. It was this mechanism that astronomers R. R. Raste and P. Maley used to explain a large lunar flash observed on March 23,1983, and other sightings as well.One problem with

4、 the satellite theory is that TLP were reported long before the advent of artificial satellites. The earliest known account comes from the twelfth-century writer Gervase. On June 18, 1178, in Canterbury, England, Gervase was observing an eclipse of the moon. He was startled by what appeared to be “a

5、 flaming torch, that spewed out fire, hot coals, and sparks“. Eighteenth-century astronomer Sir William Herschel, discoverer of the planet Uranus, also reported seeing both types of TLP.He described one TLP as looking like a piece of slowly burning charcoal. In 1830, Andrew Grant, studying the moon

6、from an observatory in Cape Town, South Africa, also observed flashing lights. He told newspaper reporters that he believed the lights came from the sun flashing off clear glass domes that covered cities and forests on the otherwise dead moon. Grant claimed in an interview that he had seen flocks of

7、 red and white birds, herds of “diminutive bison“, and strange beavers that walked on their hind legs. Not only that, but he claimed even to have seen people with batlike wings who had built towers and pyramids beneath the domes.In more recent times, a record number of TLP were monitored from 1968 t

8、o 1972, during the Apollo missions to the moon. This fact is hardly surprising given that more telescopes were probably trained on the moon during these four years than had been in the entire 270-year history of telescopic observation preceding that time. Though many sightings were dubious, some wer

9、e highly plausible because they were made by independent observers at different locations. Another notable TLP observation, and the only one confirmed by photographic evidence, took place on April 23, 1994. When over a hundred amateur astronomers reported seeing a dark red cloud spreading across a p

10、ortion of the Aristarchus crater, astronomer Bonnie Buratti of the Jet Propulsion Laboratory decided to investigate. She got access to photographs of the moon taken by the U.S. lunar mapping satellite Clementine, and indeed, these images confirmed the presence of a reddish cloud obscuring part of th

11、e crater.Even those who believe in TLP cannot agree why the moon sporadically flashes and forms clouds, but many theories have been proposed. Another possibility is that, in some places on the moon, there are chemicals that glow when they are exposed to bursts of radiation from the sun during solar

12、flares.There is, in fact, some evidence that TLP are observed more frequently during episodes of solar activity. After Project Apollo astronauts brought lunar rocks back to the earth, scientists determined that there are flammable gases inside some moon rocks. Perhaps these rocks crack open and are

13、then ignited by a stray spark, causing the flash. However, what causes these rocks to split open?One possibility is “thermal cracking“. A rock heats up in the intense sunlight.Suddenly, when the sun sets, the temperature drops, and the stone cracks. The rocks might also be shattered by “moonquakes“,

14、 seismic activity on the moon, or by meteors. Scientist R. Zito believes the flashes come not from gas trapped inside the rocks but from the crystals of the rocks themselves. If someone chews a sugar cube in a dark room, sparks appear to come from the persons mouth as the sugar crystals are crushed.

15、 Zito believes that this “sugar cube effect“ occurs when meteors smash into lunar rocks, crushing the crystals.And what about the billowing clouds? The most commonly held belief today is that they are caused by pockets of gas trapped beneath the lunar surface. The clouds may be caused by the rapid e

16、scape of these gases, which kicks up clouds of dust. The pockets of gas may be freed by moonquakes or the pockets may be punctured by meteors. （分数：13.00）(1).Which of the following statements best summarizes the overall organization of the passage? _A. A popular idea is challenged, and this challenge

17、 is then refuted.B. A generalization is made, and examples of it are examined.C. Historical information is reviewed and then the current situation is presented.D. A phenomenon is described and possible explanations for it are proposed.（分数：1.00）A.B.C.D.(2).The word “fleeting“ in the passage is closes

18、t in meaning to _.A. brightly glowing B. amazingC. short-lived D. blinking（分数：1.00）A.B.C.D.(3).The phrase “this mechanism“ in paragraph 1 refers to _.A. the flashing of sunlight off a reflective surfaceB. the windshield of an automobileC. a satelliteD. an observers telescope（分数：1.00）A.B.C.D.(4).Why

19、does the author mention the writer Gervase in paragraph 2? _A. To weaken the satellite theory of Raste and Maley.B. To document the earliest sighting of a lunar eclipse by a scientist.C. To support the ideas of Herschel and Grant.D. To provide an early theory about the causes of TLP.（分数：1.00）A.B.C.D

20、.(5).Which of these sightings is claimed to be made by Andrew Grant in paragraph 2? _A. The flocks of red and white birds.B. The bat-winged people who built towers and pyramids.C. The herds of tiny bison.D. The unusual beavers that walked on two legs.（分数：1.00）A.B.C.D.(6).Which of the following sente

21、nces best expresses the essential information in the boldface sentence below? Incorrect answer choices omit important information or change the meaning of the original sentence in an important way.In more recent times, a record number of TLP were monitored from 1968 to 1972, during the Apollo missio

22、ns to the moon, a fact that is hardly surprising given that more telescopes were probably trained on the moon during these four years than had been in the entire 270-year history of telescopic observation preceding that time.A. Because far more people were looking at the moon through telescopes duri

23、ng the Apollo missions, more TLP were seen then than had been seen during any prior period.B. From 1968 until 1972. not just amateur astronomers but also trained scientists saw more TLP than they had ever seen before.C. More TLP occurred on the moon between 1968 and 1972 than had occurred during the

24、 previous 270 years of telescopic observation.D. It is unsurprising that in the four years between 1968 and 1972 more people with telescopes were observing the moon than had observed it in the previous 270 years.（分数：1.00）A.B.C.D.(7).According to the author, an observation is more reliable when it is

25、 made by _.A. a professional astronomerB. a group of astronomers working togetherC. a number of observers working separately in different locationsD. a person observing the same part of the moon night after night（分数：1.00）A.B.C.D.(8).How was astronomer Bonnie Buratti able to “confirm“ the presence of

26、 a cloud on the moon? _A. By interviewing one hundred amateur astronomers.B. By examining satellite photography.C. By analyzing lunar rocks.D. By taking a picture through a telescope.（分数：1.00）A.B.C.D.(9).The word “stray“ in the passage is closest in meaning to _.A. speeding B. hot C. spinning D. und

27、irected（分数：1.00）A.B.C.D.(10).Which of the following situations is an example of thermal cracking as it is described in paragraph 4? _A. A dam breaks when water rises behind it.B. Sparks appear when someone chews a candy mint in a dark room.C. A cool glass breaks when it is filled with boiling water.

28、D. An ice cube melts in the heat of the sun.（分数：1.00）A.B.C.D.(11).All of the following are given as possible reasons for the cracking of moon rocks EXCEPT _.A. seismic activity B. sudden temperature changesC. the action of meteors D. the pressure of gases（分数：1.00）A.B.C.D.(12).Look at the four square

29、s, , , and （分数：1.00）A.B.C.D.(13).Directions: Select sentences from the answer choices and match them to the category to which they relate. ONE answer choice will NOT be used. This question is worth 3 points.Theories that explain_Answer ChoicesA. TLP are caused by the collision of two meteors, why TL

30、P do not exist.B. TLP are caused by the reflection of sunlight off satellites.C. TLP are caused by meteors crushing the crystals in lunar rocks.D. TLP are caused by chemicals on the surface of Theories that explain the sun that are affected by solar activity, why TLP do exist.E. TLP are caused by er

31、rors made by amateur astronomers.F. TLP are caused by the reflection of the sun off glass domes.（分数：1.00）填空项 1:_二、Passage 2(总题数：1，分数：13.00)ThermoregulationMammals and birds generally maintain body temperature within a narrow range (36-38C for most mammals and 39-42 for most birds) that is usually co

32、nsiderably warmer than the environment. Because heat always flows from a warm object to cooler surroundings, birds and mammals must counteract the constant heat loss. This maintenance of warm body temperature depends on several key adaptations. The most basic mechanism is the high metabolic rate of

33、endothermy itself. Endotherms can produce large amounts of metabolic heat that replace the flow of heat to the environment, and they can vary heat production to match changing rates of heat loss. Heat production is increased by such muscle activity as moving or shivering. In some mammals, certain ho

34、rmones can cause mitochondria to increase their metabolic activity and produce heat instead of ATP. This nonshivering thermogenesis (NST) takes place throughout the body, but some mammals also have a tissue called brown fat in the neck and between the shoulders that is specialized for rapid heat pro

35、duction. Through shivering and NST, mammals and birds in cold environments can increase their metabolic heat production by as much as 5 to 10 times above the minimal levels that occur in warm conditions.Another major thermoregulatory adaptation that evolved in mammals and birds is insulation (hair,

36、feathers, and fat layers), which reduces the flow of heat and lowers the energy cost of keeping warm. Most land mammals and birds react to cold by raising their fur or feathers, thereby trapping a thicker layer of air. Humans rely more on a layer of fat just beneath the skin as insulation; goose bum

37、ps are a vestige of hair-raising left over from our furry ancestors. Vasodilation and vasoconstriction also regulate heat exchange and may contribute to regional temperature differences within the animal.For example, heat loss from a human is reduced when arms and legs coo to several degrees below t

38、he temperature of the body core, where most vital organs are located. （分数：13.00）(1).According to paragraph 1, the most fundamental adaptation to maintain body temperature is _.A. the heat generated by the metabolismB. a shivering reflex in the musclesC. migration to a warmer environmentD. higher cal

39、oric intake to match heat loss（分数：1.00）A.B.C.D.(2).Based on information in paragraph 1, which of the following best explains the term “thermogenesis“? _A. Heat loss that must be reversed.B. The adaptation of brown fat tissue in the neck.C. The maintenance of healthy environmental conditions.D. Condi

40、tions that affect the metabolism.（分数：1.00）A.B.C.D.(3).Which of the sentences below best expresses the information in the highlighted statement in the passage? The other choices change the meaning or leave out important information.A. An increase in heat production causes muscle activity such as movi

41、ng or shivering.B. Muscle activity like moving and shivering will increase heat production.C. Moving and shivering are muscle activities that increase with heat.D. When heat increases, the production of muscle activity also increases.（分数：1.00）A.B.C.D.(4).The word “minimal“ in the passage is closest

42、in meaning to _.A. most recent B. most active C. newest D. smallest（分数：1.00）A.B.C.D.(5).In paragraph 2, the author explains the concept of vasodilation and vasoconstriction by _.A. describing the evolution in our ancestorsB. giving an example of heat loss in the extremitiesC. comparing the process i

43、n humans and animalsD. identifying various types of insulation（分数：1.00）A.B.C.D.(6).The word “regulate“ in the passage is closest in meaning to _.A. protect B. create C. reduce D. control（分数：1.00）A.B.C.D.(7).According to paragraph 3, why do many marine animals require a layer of blubber?A. Because ma

44、rine animals have lost their hair during evolution.B. Because heat is lost in water twice as fast as it is in air.C. Because dry hair does not insulate marine animals.D. Because they are so large that they require more insulation.（分数：1.00）A.B.C.D.(8).The word “those“ in the passage refers to _.A. ma

45、rine animals B. core temperaturesC. land mammals D. metabolic rates（分数：1.00）A.B.C.D.(9).Why does the author mention chickadees in paragraph 4? _A. To discuss an animal that regulates heat very well.B. To demonstrate why chickadees have to eat so much.C. To mention an exception to the rules of thermo

46、regulation.D. To give a reason for heat production in small animals.（分数：1.00）A.B.C.D.(10).in paragraph 6, the author states that evaporative cooling is often accomplished by all of the following methods EXCEPT _.A. by spreading saliva over the areaB. by urinating on the bodyC. by panting or flutteri

47、ng a pouchD. by immersing themselves in water（分数：1.00）A.B.C.D.(11).The word “enhance“ in the passage is closest in meaning to _.A. simplify B. improve C. replace D. interrupt（分数：1.00）A.B.C.D.(12).Look at the four squares, , , and （分数：1.00）A.B.C.D.(13).Directions: An introduction for a short summary

48、of the passage appears below. Complete the summary by selecting the THREE answer choices that mention the most important points in the passage. Some sentences do not belong in the summary because they express ideas that are not included in the passage or are minor points from the passage. This quest

49、ion is worth 2 points.Thermoregulation is the process by which animals control body temperatures within healthy limits._A. Although hair can be a very efficient insulation when it is dry and it can be raised, hair becomes ineffective when it is submerged in cold water.B. Some animals with few adaptations for thermoregulation migrate to moderate climates to avoid the extreme weather in the polar regions and the tropics.C.