鱼+ 水= 复数还是单数 动词？？？

        In the most common procedure for harvesting forage crops such as alfalfa, as much as 20 percent of the leaf and small-stem material, which is the most nutritious of all the parts of the plant, shattered and fell to the ground.

(A) which is the most nutritious of all the parts of the plant, shattered and fell

(B) the most nutritious of all parts of the plant, shatter and fall

(C) the parts of the plant which were most nutritious, will shatter and fall

(D) the most nutritious parts of the plant, shatters and falls（D）

(E) parts of the plant which are the most nutritious, have shattered and fallen

像上面这种两种不可数名词相加的形式， 记得以前好像是说后面用复数动词？ 请大家给看看为什么这道题这样呢？

这里的未划线部分用的是much，表明后面是不可数，所以用单数。

rhod讲的很好.

不过我还是有和麻集爱一样的问题: 我也记得像上面这种两种不可数名词相加的形式，后面用复数动词.这里为什么把它看单数? 当然做题可以用rhod的方法, 但要是我们自己写, 怎样判断该用复数还是单数?

这道题又考到了much of...

much of +名词单数

most of +名词复数