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

A.for whom

B.of whom

C.with which

D.in which

答案及解析： B

解题思路：本题属于非限定性定语从句．句意指人，可先排除A、C两项．把该句分解成两个独立的句子：The course normally attract 20 students per year；up to half of them will be from overseas.可以看出，half后应接of them．