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

The process of elimination:

COMMA + Which:

In the GMAT land, whenever we use "which", we MUST use COMMA before "WHICH".

--> This rule eliminates the C and E.

X% of Y:

X% of Y will be singular if Y is singular and will be plural if Y is plural.

20% of leaf and small-stem is singular because Y part, leaf and small-stem, is singular.

-->This eliminates B.

Appositive concept:

When we use appositive, we never use "which is ..."

Example:

We need to buy a powerful motherboard, which is the central printed circuit board in many modern computers, to enhance the quality of work. --INCORRECT

Revised:We need to buy a powerful motherboard, the central printed circuit board in many modern computers, to enhance the quality of work. ---CORRECT.

Mr. Amartya Sen, who is an economist, has visited the project. --INCORRECT.

Revised: Amartya Sen, an economist, has visited the project.--CORRECT.

We never use "which is.../Who is" in the appositive.

Option A has used "which is ..." in the appositive. So, it is NOT correct.

Answer is D.

Well everything is correct except
"20% of leaf and small-stem is singular because Y part, leaf and small-stem, is singular."
this is the major problem in the sentence as you can read in the comments. It's not so trivial to see it is singular. (the word 'and' is joining two singular nouns to plural one)
the reason it is singular is that the word "material" appears at the end of the "leaf and small-stem". That's what someone told here. I guess it is correct.

eladoren wrote:Well everything is correct except
"20% of leaf and small-stem is singular because Y part, leaf and small-stem, is singular."
this is the major problem in the sentence as you can read in the comments. It's not so trivial to see it is singular. (the word 'and' is joining two singular nouns to plural one)
the reason it is singular is that the word "material" appears at the end of the "leaf and small-stem". That's what someone told here. I guess it is correct.

Good to see it.

I appreciate it.

Thanks.

eladoren wrote:Well everything is correct except
"20% of leaf and small-stem is singular because Y part, leaf and small-stem, is singular."
this is the major problem in the sentence as you can read in the comments. It's not so trivial to see it is singular. (the word 'and' is joining two singular nouns to plural one)
the reason it is singular is that the word "material" appears at the end of the "leaf and small-stem". That's what someone told here. I guess it is correct.

The subject here is material (How do we know? Because the non-underlined portion says : material and not materials).

Material is always singular; and if material is singular, 20% of the material would also be singular.

Ok. Now how do we know that material is the subject and not leaf and small-stem.

Well, that's because the only plausible way to read it is: 20 % of the (leaf and small-stem) material.

Well this is a pretty old post, but I am still confused.

In answer D, what does "the most nutritious parts" refer to? If the subject of the sentence is singular, why use PARTS instead of PART? This is where answer D threw me off!

Please help!