54. The cause of the cold weather in England from 1815 to 1818 was　　 .

A. drop of average temperature by 4.5.F

B. volcanic ash in the atmosphere

C. pollution caused by the Industrial Revolution

D. increased heat reflection from the land to space

53. The effect of Tambora’s eruption was 　　　　.

A. felt mainly in the Dutch East Indies 　　　　　　 B. of a several day period worldwide

C. evidence of pollution’s cooling the earth 　　 D. immediately clear to the world ’s scientists

52. The word “effect” in Paragraph 1 is closest in meaning to“　　 ”.

A. begin with　 　　　　 B. result from　 　　　　　 C. act on　 　　　　　 D. bring about

51. From the passage, which of the following is thought to be the reason for sleep-deficit?

　 A. The light bulb was invented.

　 B. People have to work harder than they used to.

　 C. People have more time to relax themselves at night.

　 D. Shorter-hour sleep can make people more energetic.

D

Scientists say that air pollution causes downfall in the world’s average air temperature. In order to prove that theory, ecologists(生态学家)have turned to historical facts in relation to especially huge volcanic eruptions(喷发).They suspect that volcanoes effect weather changes that are similar to air pollution.

One source of information is the effect of the eruption of Tambora, a volcano in Sumbawa, the Dutch East Indies, in April 1815.The largest recorded volcanic eruption, Tambora threw 150 million tons of fine ash into the air. The ash from a volcano spreads worldwide in a few days and remains in the air for years. Its effect is to turn incoming solar radiation back into space and thus cool the earth. For example, records of weather in England show that between April and November 1815,the average temperature had fallen 4.5⁰F. During the next twenty-four months, England suffered one of the coldest periods of its history. Farmer’s records from April 1815 to December 1818 indicate frost throughout the spring and summer and sharp decreases in crop and farm animal markets. Since there was a time of several years between cause and effect, by the time the world agricultural product community had worsened, no one realized the cause.

Ecologists today warn that we face a double threat. The ever-present possibility of volcanic eruptions, such as that of Mt. St. Helens in Washington, added to man’s pollution of the atmosphere with oil, gas, coal, and other polluting substance, may bring us increasingly colder weather.

50. It can be concluded from the passage that one should sleep as many hours as necessary to 　　　　　.

　 A. improve one’s memory dramatically　 　　　　　 B. be considered dynamic by other people

　 C. maintain one’s daily schedule　　 　　　　　　 D. feel energetic and perform adequately

49. Many Americans believe that 　　　　　　.

　 A. sleep is the first thing that can be sacrificed(牺牲)when one is busy

　 B. they need more sleep to deal with the complexities of everyday life

　 C. to sleep is something one can do at any time of the day

　 D. enough sleep promotes people’ drive and ambition

48. According to Dr. David, Americans 　　　　　　.

　 A. are ideally vigorous even under the pressure of life

　 B. often neglect(忽略)the consequence of sleep deficit

　 C. do not know how to relax themselves properly

　 D. can get by on 6.5 hours of sleep

47. The best title for this passage is 　　　　　.

　 A. Jogging and Diet　　　　 　　　　　　　　　　　 B. Exercise and Health

　 C. Physical Fitness　　　　 　　　　　　　　　　　 D. Life Expectancy and Diet

C

Judging from the recent surveys, most experts in sleep behavior agree that there is virtually an epidemic(流行病)of sleepiness in the nation. “I can’t think of a single study that hasn’t found Americans getting less sleep than they ought to,” says Dr David. Even people who think they are sleeping enough would probably be better off with more rest.

The beginning of our sleep-deficit(睡眠不足)crisis can be traced to the invention of the light bulb a century ago. From diary entries and other personal accounts from the 18^thand 19^th centuries, sleep scientists have reached the conclusion that the average person used to sleep about 9.5 hours a night. “The best sleep habits once were forced on us, when we had nothing to do in the evening down on the farm, and it was dark.” By the 1950s and 1960s, that sleep schedule had been reduced dramatically, to between 7.5 and eight hours, and most people had to wake to an alarm clock. “People cheat on their sleep, and they don’t even realize they’re doing it,” says Dr David. “They think they are okay because they can get by on 6.5 hours, when they really reached 7.5, eight or even more to feel ideally vigorous(体力充沛的).”

Perhaps the most merciless robber of sleep, researchers say, is the complexity(复杂性)of the day. Whenever pressure from work, family, and friends. Many people consider sleep the least expensive item on his program. “In our society, you’re considered dynamic if you say only need 5.5 hours’ sleep. If you’ve got to get 8.5 hours, people think you lack drive and ambition.”

To determine the consequence(结果)of sleep-deficit, researcher have put subjects through a set of psychological and performance tests requiring them, for instance, to add columns of numbers or recall a passage read to them only minutes earlier. “We’ve found that if you’re in sleep deficit, performance suffers, ”says Dr. David. “Short-term memory is weakened, as are abilities to make decisions and to concentrate.”

46. It is implied but not stated that 　　　　　.

　 A. heart disease is the number one killer among Americans

　 B. exercise and dieting bring about spiritual as well as physical well-being

　 C. people don’t stay on a diet because it doesn’t work

　 D. a 20-pound weight loss within two weeks is too much for the body

45. According to the passage, which of the following statements is TRUE?

　 A. Jogging can damage the body because it is too tough an exercise.

　 B. Diets are so popular because they are on the best-seller lists.

　 C. Americans now live to be 73 years old.

　 D. Exercise and diet are more widespread in America than ever before.