问题补充：
Xiao Li is said abroad, but I don’t know what country he studied in.
A. to study
B. to be studying
C. to be studied
D. to have studied
答案：
A. to study
B. to be studying
C. to be studied
(答案→)D. to have studied
解析：如果将题干改成下列句子：It is said that Xiao Li abroad, but I don’t know what country he studied in.上下句谓语动词发生的时间关系就一目了然：很显然“留学”应该发生在过去。It is said that Xiao Li studied abroad, but I don’t know what country he studied in.转换成：Xiao Li is said to have studied abroad, but I don’t know what country he studied in.动词不定式的完成式除了表示“完成(Xiao Li is said to have gone abroad.据说小李已经到国外去了)”，还可以表示“过去”。如果将下文改成“but I don’t know what country he is studying in”则备选项B就是正确答案了。
句意：据说小王在国外留过学，但是我不知道他在什么国家学习过。
