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
句意: 直到这位学生计算此数学题超过一小时我才会告诉他答案。主句为一般将来时, 时间/条件/让步状语从句的谓语动词用现在时表将来, 因此A正确。
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