2. 考研
  3. How much sleep does a person need?【C1】______the physiological bases of the need for sleep remain conjectural(猜想), rendering conc

How much sleep does a person need?【C1】______the physiological bases of the need for sleep remain conjectural(猜想), rendering conc

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问题     How much sleep does a person need?【C1】______the physiological bases of the need for sleep remain conjectural(猜想), rendering conclusive answers to this question impossible, much evidence has been gathered on how much sleep people do in fact obtain. Perhaps the most important conclusion to be【C2】______from this evidence is【C3】______there is great variability among individuals in total sleep time. For adults,【C4】______between six and nine hours of sleep as a nightly average is not unusual, and 7.5 hours probably best expresses the norm. Such norms, of course, forms inevitably vary with the criteria of sleep employed. The most【C5】______and reliable figures on sleep time, including those cited here, come from studies in sleep laboratories, where EEG criteria are employed.
    【C6】______consistently has been associated with the varying amount, quality, and pattern of electrophysiologically defined sleep. The newborn infant may spend an average of about 16 hours of each 24-hour period in sleep,【C7】______the sleep time drops sharply: by two years of age, it may【C8】______from nine to 12 hours. Decreases to approximately six hours have been observed among the elderly.
    【C9】______will be discussed from below, EEG sleep studies have indicated that sleep can be considered to consist of several different stages. Developmental changes in the relative proportion of sleep time【C10】______in these sleep stages are as striking as age-related changes in total sleep time.
【C3】
选项 A、how
B、what
C、whether
D、that
答案D
解析 本题的考点是表语从句引导词，后面there be从句语义完整，无须任何添加，故选择一个起语法作用的引导词that即可。
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