Robert is said abroad but I don’t know which country he studied in.A. to have studiedB.

问题补充：

Robert is said abroad, but I don’t know which country he studied in.

A. to have studied

B. to study

C. to be studying

D. to have been studying

答案：

(答案→)A. to have studied

B. to study

C. to be studying

D. to have been studying

解析： study这一动作发生在主句谓语之前，所以用不定式的完成时；且but I don’t know which country he studied in.说明他已经不在国外学习了，所以选A。