为什么不是both them而是both of them

为什么不是both them而是both of them both them还是both of them?为什么? both of them翻译 请问both of them为什么错了? both of them与both of whom Both of them study very hard.为什么要用them? 1.Both of them are_______. Both of them a student both of them both them both of their parents both their pare Both of ___(they,them)are good at runing.为什么不是THEY? both of them能换成both them吗?另外both是什么词性? Both of them 与 all of them要如何区分