题目内容
It puzzles the scientists _____ some mammals produce their young _____ others lay eggs.
| A．that; while | B．what; while | C．that; as | D．what; as |
A
解析试题分析：本句中的it是形式主语 ，真正的主语是后面that引导的主语从句，that在主语从句中不充当任何成分，只起引导作用。第二空的连词while然而，表示上下文轻微的转折关系。As不能表示上下文的转折关系。句义：让一些科学家困惑的是一些哺乳动物生出下一代，而另外一些却产卵。故A正确。
考点：考察主语从句和连词辨析
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| A．unless | B．before | C．until | D．while |
How can you expect to learn anything ______ you spend all your time playing computer games?
| A．unless | B．until | C．though | D．when |
It just isn’t fair that____I was working as a waiter last month, my friends were lying on the beach.
| A．while | B．whenever | C．though | D．for |
——Did you stay up very late last night?
——No，It was not 10 o’clock yet ____I went to bed.
| A．when | B．until | C．that | D．while |
______ the day went on, the weather got worse.
| A．With | B．Since | C．While | D．As |
Provide your doctor with a detailed medical history ____he can give you the accurate treatment
| A．even if | B．in case | C．so that | D．as though |
Of all the books on the desk, _____is of any use for our study.
| A．no one | B．nothing | C．none | D．neither |
It may be 5 or 10 years __________ it is possible for people to find a space station on the moon.
| A．since | B．before | C．after | D．when |