Mark was a student at this university from 1999 to he studied very hard and was m

问题补充：

Mark was a student at this university from 1999 to , , he studied very hard and was made Chairman of the Students Union.

A. during which time

B. for which time

C. during whose time

D. by that time

答案：

(答案→)A. during which time

B. for which time

C. during whose time

D. by that time

解析：1997到为一阶段时间，所以用“during which time”引导定语从句，表示“在此期间”。