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  3. Throughout history man has observed such natural cycles as the rising and setting of the sun, the ebb and flow of the ocean tide

Throughout history man has observed such natural cycles as the rising and setting of the sun, the ebb and flow of the ocean tide

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问题     Throughout history man has observed such natural cycles as the rising and setting of the sun, the ebb and flow of the ocean tides, and the changes of the seasons. The【C1】______nature of these events provided people with a measure of【C2】______about things to come and give them reason to reflect on their past and plan for their future. The regularity of such social activities as work hours, meal times, and holiday schedules【C3】______the extent to which human activity itself is organized in cycles.
    Recently,【C4】______effort has been spent investigating the effect of various biological rhythms in the human body.【C5】______, interest in these rhythms at least in part results from man’s basic desire to predict future behavior.
    The human body【C6】______a number of repeatable rhythms: heartbeats, breathing rates, brain waves and other physiological processes within the human machine.
    Scientists studying rhythms in humans have measured sleep patterns and attention【C7】______over periods of several days, and have【C8】______the fact that the cycles exist and exert effects on physiological and sociological behavior. A common example is jet lag. A person’s traveling in the east-west direction across time zones【C9】______his sleep cycles—it may take several days to return to the【C10】______cycle or to readjust to a new one.
A)indicates E)considerable I)Certainly M)security
B)demonstrated F)upsets J)Thankfully N)exhibits
C)verifying G)disappoints K)spans O)limits
D)normal H)periodic L)gorgeous
【C8】
选项
答案B
解析 这里缺少谓语动词，根据空格前的have可判断时态是现在完成时。词库中只有demonstrated是过去分词形式，带入后表示“……证明了一个事实”。
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