02-01-38, help!

38. During the nineteenth century the molecular theory of matter was developed,

which considered all matter to be composed of tiny, indivisible entity

A              B             C                    D

called molecules.

Answer D.

I understand why D is wrong, but am wondering why  B is correct. Shouldn't it be " all matters"?

但是matter 有时好像又是matters

怎么分啊?

water有时也有waters啦

要根据情况而定的,首先要做的就是理解题意,看看此词是否可数,是单是复,等等...