GMAT Sentence Correction (SC) | In the most common procedure for harvesting forage crops

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) themost nutritious of all parts of the plant, shatter and fall
(C) theparts of the plant which were most nutritious, will shatter and fall
(D)the most nutritious parts of the plant, shatters and falls