题目内容
________ there are living creatures in the outer space as those on Earth hasn't been proved until now.
| A.How | B.When |
| C.Where | D.Whether |
D
D 考察主语。句意:在外部空间是否有与地球相同的生物直到现在还没有得到证明。Whether引导主语从句,意为是否。
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