Why did they keep trying they must have known it was hopeless?A.ifB.becauseC.whe
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Why did they keep trying _________ they must have known it was hopeless?
A.if
B.because
C.when
D.whether
试题答案
C
这题考查连词的用法，when表示“既然”句意是：既然他们已经知道是无望了，为什么还要一直尝试呢？选C。