我自己研究了半天，总结出来是有谓语动词用which 没有谓语动词用them .这里的谓语动词我理解为am is are have has had was were 即空格后看到这些词选which 看不到选them 。
可我做题还是错了！我要烦死了！到底要怎样嘛？我搞这问题很久了！
⑴I was given three books on cooking ,the first ( )I really enjoyed .
这为什么选of which 而不是of them 呢？我没看到我心中的谓语啊！
⑵There are two buildings , ( )stands nearly a hundred feet high .
这又为什么选the larger of which 而不是the larger of them 呢？谓语呢？
求帮忙啊我后天就期末考了第一门就考英语啊！！！！！！
which, 与 that-, who-/whom, 都属于“关系代词”，关系代词是与复合句有关的，是用来引导定语从句的。
them,与 he/she, it, you I me, us等属于同一的概念范畴，是普通的人称代词，代替前面提到的人或物，避免重复提及前面已经提过的相同的名词。
所以，判断的关键，是要从句子的结构入手，看这个句子：
1、简单句1。简单句2。用 them.
I teach 40 students. Twenty of them are girls.
2. 并列句：简单句1 and 简单句2。用them.
I teach 40 students and twenty of them are girls.
3. 复合句：主句+ 关系代词(which) + 定语从句。
I teach 40 students (,) twenty of which/ whom are girls.
明白了？
来看你的句子：
1、2句和我的3句是一样的，主句+ 非限制性定语从句，用关系代词，which-
但是一旦改变你的句子结构，表达就会改变：
I was given three books on cooking. I really enjoyed the first ( of them ) .
两个独立的简单句，用人称代词，them.
I was given three books on cooking and I really enjoyed the first （of them).
用 and 连接的一个并列句，用人称代词：them.追问
He planned to write 3 books about math, but ______ never published.选项中有all of them 跟all of which 可以选，结果答案是all of which。敝人实在难以分辨其差别，有没有哪位仁兄可教我？
另外还有一例句如下：
His notebooks were filled with fantastic inventions and machines, but ______ were built.
同样也有few of them和few of which 可以选，这次答案却是few of them...
那这个怎么解释呢？同样有连词but
He planned...,but....never ...
和我讲的用 and 连接的并列句是一样的，but 也是并列连词，表示转折罢了。
你说该选哪个？
下一句也一样，因为也是 but 连接的。
考虑好后立马给我答复，看你是否理解并会运用了。
如：
Thomas is one of the boys who are fond of sports.
I know a boy who is good at surfing the Internet.
Adults don't like children who tell lies.
