Question

Dr．Zhou is said ________ abroad when he was in his twenties．

[　　]

A．

to have studied

B．

to study

C．

to be studying

D．

to have been studying

Answer 1

答案：A
解析：

to have studied表示動(dòng)作發(fā)生在主句的謂語(yǔ)之前。