The course normally attracts 20 students per year, ________ up to half will be from overseas．
A.for whomB.of whomC.with whichD.in which在线课程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．