问题补充:
Robert is said abroad, but I don’t know what 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:根据句中的 studied 可知,他曾到国外留过学,也就是说“留学”这个动作已结束并发生在谓语动作(is said)之前,故用完成式,即选 A。