The course normally attracts 20 students per year up to half are from abroad.A. of whomB

问题补充：

The course normally attracts 20 students per year, up to half are from abroad.

A. of whom

B. for whom

C. in which

D. with whom

答案：

(答案→)A. of whom

B. for whom

C. in which

D. with whom

解析：考查定语从句。这里要弄清先行词为20 students，后跟“介词+whom”结构。