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“通過……方式”，如果吧means作爲先行詞，後面定語從句就要有by，這句話意思是“生物鐘指的是生物調節其行爲的方式”。
2.^the time – to。adjust A to B 指A適應B，這句指“在沒有任何提示的'情況下，是自己的行爲方式適應外界的時間”。
ors^--which/ that。這是一個定語從句，修飾factors，which/that做主語不能省略。
ks—clock’s
（第二個）--for。account for意思是explain，爲固定詞組。
6.^an—as 。這句話意思是“這些是由於對規律環境的適應進化而來的”。
—of。be independent of 意思是“獨立於……，不依賴……”
ged—changing。文章要表達的是“變化着的長度”，應該用現在分詞。
9. up去掉或者將up改爲that。hold本身就有“持……觀點”的意思。
10. potential—potentially
