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  3. Every living thing has what scientists call a biological clock that controls behavior. It tells plants when to form flowers and

Every living thing has what scientists call a biological clock that controls behavior. It tells plants when to form flowers and

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问题     Every living thing has what scientists call a biological clock that controls behavior. It tells plants when to form flowers and insects when to leave protective cocoon(茧) and fly a-way. And it tells animals and human beings when to awaken, sleep, and seek food. It controls our body temperatures, the release of some hormones(激素)and even dreams.
    Events outside the plant and animal affect its actions. Scientists recently found that a tiny animal called Siberian hamster (大仓鼠) changes the color of its fur because of the num-ber of hours of daylight. In shorter days of winter its fur becomes white. The fur becomes gray-brown in longer hours of daylight in summer.
    Inner signals control other biological clocks. German scientists found that some internal one seems to order birds to begin their migration flights two times each year. Birds prevented from flying become restless when it is time for the trip. But they become calm again when the time of the flight has ended.
    A mix of outside and internal events controls some biological clocks; such things as heartbeat and the daily change from sleep to walking take place because of both external and internal signals.
    Scientists are beginning to learn which parts of the brain contain the biological clocks. A researcher at Harvard University—Dr. Martin Moore Ede—said a small group of cells near the front of the brain seems to control the timing of some of our actions. Probably there are other cells to control other body activities. He is studying how they affect the way we do our work. Most of us have great difficulty if we must often change to different work hours. It can take many days for a human body to accept a major change in work hours. Industrial officials should have a better understanding of biological clocks and how they affect workers. He said such an understanding could reduce sickness and accidents at work, and would help increase production.
From the passage we can infer that______.
选项 A、biological clocks are responsible for all the human behaviors
B、biological clocks are too mysterious to be explained
C、heartbeat and some daily activities affect biological clocks
D、studies on biological clocks can throw some light on human actions
答案D
解析 文章从生物钟对动植物的影响谈起，进而谈到科学家们对人脑中包含生物钟部分的研究以及这一研究对人类行为的影响等。因此可以推断出D是正确答案。
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