题目内容
I won't tell the student the answer to the math problem until he ____on it for more than an hour.
A. has been working B. will have worked
C. will have been working D. had worked
A.
解析:时态即将来完成时进行时用于时间状语从句。依据句意可以看出要等学生做一个小时才给答案。因为有until引导,所以在状语从句中只能用现在完成一般时代替。
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