He could speak English fluently because he it for four years when he was a college studen

问题补充：

He could speak English fluently because he it for four years when he was a college student.

A. had studied

B. have been studying

C. studied

D. was studying

答案：

A. had studied

B. have been studying

(答案→)C. studied

D. was studying

解析：考查时态：句意：他的英语可以说的很流利，因为他做大学生的时候学习了四年。说明学习英语是在大学当学生的时候，用过去时。选C。