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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

admin2012-06-02  55
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 aging 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 语义理解题。要结合上下文来判断。这一句的上文提到实验对象与外界隔离，下文提到实验过程中实验对象无法知道时间，由此可以推断，实验对象因不知道具体时间只得靠自己的内部生物钟生活，即他们要完全按照自己的生理节律生活，故[A]为答案。其余三项都与文意不符。
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