需要有解释.

问题描述:

需要有解释.
1 He was very rude to the Custom officer,___of course made things even worse.
A who B whom C what D which
2 Is this the factory____you visited the other day?
A that B where C in which D the one
3 China has thousands of islands.___Hainan Island is the largest.
A of them B among which C one of which D among them
4 Who__knows him would trust him?
A whom B that C which D who

1选D.
which指代前面这句话的这件事(使事情更糟),定语从句.
2选A.
前面有先行词factory就不能用地点副词where和指代短句the one,而in which=where,
that引导非限定性定语从句.
3选A.
首先,前面形成一句话(句末句号,故下句不是定语从句,排除B和C);然后*应该接的是介词of.
4选B.
先行词是疑问副词who,这一类均只能用that引导定语从句.