og 78题的疑问

78. The root systems of most flowering perennials either become too crowded, which results in loss in vigor, and spread too far outward, producing a bare center.

(A)  which results in loss in vigor, and spread

(B)   resulting in loss in vigor, or spreading

(C)  with the result of loss of vigor, or spreading

(D)  resulting in loss of vigor, or spread

(E)   with a resulting loss of vigor, and spread

Choice A misuses which: as a relative pronoun, which should refer to a specific noun rather than to the action of an entire clause.

对于A的解释,这不是一个非限制性定语从句吗,为什么which 不能指前面整个句子?