请问all of which和all of them的区别
问题描述：
请问all of which和all of them的区别
之前做题目看到如下例句：
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...
答
all of which 意思是这些书中无论哪一个（ 常在后面跟否定词 ）
all of them 意思是所有的这些书（用于肯定语句）
下面的道理是一样的