选择He learns_by making things.

问题描述:

选择He learns_by making things.
A.lot B.lots C.a lot D.a lot of
Which do I choose?Why?(应该选哪个?为什么?)
对了,这四个有什么区别?

C为什么选Clot和lots一般不单独使用;a lot of 后必须接名词。