2. 外语
  3. Electronic Waste It has been known since ancient times that certain plants regularly open their leaves in daytime and close

Electronic Waste It has been known since ancient times that certain plants regularly open their leaves in daytime and close

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问题                         Electronic Waste
     It has been known since ancient times that certain plants regularly open
their leaves in daytime and close them at night. It was assumed which this         【S1】______
periodic change was triggered by the alternating sunlight and darkness. Such
leaves stick to their daily routine even when keeping in constant darkness.        【S2】______
    What is circadian rhythm? Many biological processes follow a 24-hours          【S3】______
schedule. These cycles are called circadian rhythms. These innate rhythms are
governed by sophisticated chemical mechanisms can be described as biological       【S4】______
clocks. Such rhythms are important for humans too! We sleep through most
of the hours of darkness and are awaken through most of the hours of               【S5】______
daylight. Body temperature increases during the day and decreases during the
night. The secretion of various hormones that controls life’s processes rises      【S6】______
and falls to a circadian rhythm.
    How does this relate to health? Circadian rhythms are important for
desirable functioning of the processes vital to health. This is most effectively
illustrated and the normal circadian rhythms are disrupted by lack of sleep or     【S7】______
by crossing time miles. It may take days or even hours for all the bodies          【S8】______
circadian rhythms to read just appropriately. The turmoil (混乱) that results
from the readjustment process when time zones are crossed experienced as the       【S9】______
phenomenon of jet lag. This is also experienced by people who do shift work.
Understanding circadian rhythms may be irrelevant to the understanding and         【S10】______
treatment of disease. Therapy can be more effective and toxic effects reduced
when drugs are administered at carefully selected times of the day.
【S1】
选项
答案which→that
解析 从语法结构看，句中的it是形式主语，真正的主语是assumed后边的主语从句。而该主语从句中不缺任何成分，所以应该用that引导。
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