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
网友回答
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。