The term biological clock is applied to the means which living __1__ things adjust their activity patterns, without any obvious cue, the __2__ time of day, or the month, or the year. They are affected but little,if at all, by drugs, chemicals, or wide temperature differences—factors may alter substantially the rates of all ordinary processes of __3__ the body.
The nature of the biological clocks mechanism is still a mystery __4__ two quite different theories have been advanced to account to __5__ them. According to the first of these theories, each individual have envolved, aided by natural selection, an adaptation to the rhythmic __6__ environment. It has now become independent on the environment __7__ according to this view, the clocks are not perfect timers.
They require regular corrections by the natural light and tide cycles and the changed lengths of the day throughout the year. __8__ The other theory holds up living things react continuously to __9__ their rhythmic physical environment. The setting of their biological clocks, therefore, involves a constant adjustment to subtle clocks which are potential perfect times. __10__
答案
1.^which—by。by the means of 指“通过……方式”，如果吧means作为先行词，后面定语从句就要有by，这句话意思是“生物钟指的是生物调节其行为的方式”。
2.^the time – to。adjust A to B 指A适应B，这句指“在没有任何提示的情况下，是自己的行为方式适应外界的时间”。
3.factors^--which/ that。这是一个定语从句，修饰factors，which/that做主语不能省略。
4.clocks—clock’s
5.to（第二个）--for。account for意思是explain，为固定词组。
6.^an—as 。这句话意思是“这些是由于对规律环境的适应进化而来的”。
7.on—of。be independent of 意思是“独立于……，不依赖……”
8.changed—changing。文章要表达的是“变化着的长度”，应该用现在分词。
9. up去掉或者将up改为that。hold本身就有“持……观点”的意思。
10. potential—potentially
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