He English for six years by the time he takes his examination.A. was studyingB. would hav

问题补充：

He English for six years by the time he takes his examination.

A. was studying

B. would have been studying

C. had been studying

D. will have been studying

答案：

A. was studying

B. would have been studying

C. had been studying

(答案→)D. will have been studying

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