The course normally attracts 20 students per year,___up to half will be from overseas.

题目

The course normally attracts 20 students per year,___up to half will be from overseas.
选项：A.in which B.for which C.with which D.of whom

答案

D.of whom
先行词是students
把先行词代入从句,句子是
up to half 【of the students】will be from overseas.
他们中的一半来自海外
所以把【of the students】换成连接词就是 of whom