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  3. Every living thing has an inner biological clock that controls behavior. The clock works all the time; even when there are no ou

Every living thing has an inner biological clock that controls behavior. The clock works all the time; even when there are no ou

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问题     Every living thing has an inner biological clock that controls behavior. The clock works all the time; even when there are no outside signs to mark the passing of time. The biological clock tells plants when to form flowers and when the flowers should open. It tells insects when to leave the protective cocoon and fly away. And it tells animals when to eat, sleep and wake. It controls body temperature, the release of some hormones and even dreams. These natural daily events are circadian rhythms.
    Man has known about them for thousands of years. But the first scientific observation of circadian rhythms was not made until 1729. In that year a French astronomer, Jean Jacques d’Ortous de Mairan, noted that one of his plants opened its leaves at the same time every morning, and closed them at the same time every night. The plant did this even when he kept it in a dark place all the time.
    Later scientists wondered about circadian rhythms in humans. They learned that man’s biological clock actually keeps time with a day of a little less than 25 hours instead of the 24 hours on a man-made clock.
     About four years ago an American doctor, Eliot Weitzman, established a laboratory to study how our biological clock works. The people in his experiments are shut off from the outside world. They are free to listen to and live by their circadian rhythms. Dr. Weitzman hopes his research will lead to effective treatments for common sleep problems and sleep disorders caused by ageing and mental illness.
    The laboratory is in the Montefiore Hospital in New York City. It has two living areas with three small rooms in each. The windows are covered, so no sunlight or moonlight comes in. There are no radios or television receivers. There is a control room between the living areas. It contains computers, one-way cameras and other electronic devices for observing the person in the living area. A doctor or medical technician is on duty in the control room 24 hours a day during an experiment. They do not work the same time each day and are not permitted to wear watches, so the person in the experiment has no idea what time it is.
    In the first four years of research, Dr. Weitzman and his assistant have observed 16 men between the ages of 21 and 80. The men remained in the laboratory for as long as six months. Last month, a science reporter for “The New York Times” newspaper, Dava Sobel, became the first woman to take part in the experiment. She entered the laboratory on June 13th and stayed for 25 days. Miss Sobel wrote reports about the experiment during that time, which were published in the newspaper.
The sentence “They are free to listen to and live by their circadian rhythms.” (Line 2-3, Para. 4) probably means
选项 A、they can live by their biological clocks without referring to man-made ones.
B、they can listen to rhythms of biological clocks and live close to them.
C、they can live their lives by regulating their own circadian rhythms.
D、they are free from the annoying rhythms of everyday life.
答案A
解析 推理判断题。文章第一句提到每种生物都有一个控制其行为的内部生物钟。第二句指出这个生物钟在不停地运作。接下来的几句话提到生物钟对植物、昆虫、动物的种种活动所起的作用。因此，不难看出，第一段的内容可概括为[D]。[A]、 [B]两项属细节内容，不足以概括段落大意；[C]是对首段尾句的错误理解。
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