All his attempts to unlock the door were , because he was using the wrong key._刷题宝

题干

All his attempts to unlock the door were , because he was using the wrong key.

A．in return

B．in vain

C．in doubt

D．in time

上一题下一题 0.85难度单项选择更新时间:2010-07-23 11:25:48

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