It is not until 1997 he entered university.A. whichB. thatC. whenD. since

问题补充：

It is not until 1997 he entered university.

A. which

B. that

C. when

D. since

答案：

A. which

(答案→)B. that

C. when

D. since

解析：这是一个强调句。强调句的句型是“It is(was)...that(who)...”。