Question

the course normally attracts 30 students every year,----up to half will be from overseas.

A.in which
B.for whom
C.with which
D.of whom

Answer 1

答案是D.of whom

这句话还原的话就是
the course normally attracts about 20 students per year.
up to half of the student will be from overseas.
这里是一个定语从句，
,of whom up to half will be from overseas.为从句，引导词为 whom,因为被修饰的词为人,故不能用which.
一般类似这样的句子最好都把它们还原,看看句子中缺不缺成分,或者介词是否正确。
比如这个句子如果用for whom，还原之后句子就变成了
up to half for the student will be from overseas.
这里介词for就明显不对了。

Answer 2

The course normally attracts 30 students every year, (of whom) up to half will be from overseas.
答案是 （D）of whom.
30 students 要跟 of whom。

Answer 3

The course normally attracts 20 students per year, _ up to half will be from overseas. 选项: a、in which b、 for whom c、 with which d