摘自曼哈顿论坛： A bit of a red herring - you could technically construct the sentence correctly either way. I'd prefer the "an increase in their use" however because that emphasizes the distinction I'm trying to make - the key point is the increase, and this is emphasized by making "the increase" the subject. But I'd go look for other, more definitive grammar errors first before deciding on this.

Luci correctly points out a distinction between "such as" and "like" in the answers. Such as means "for example" - like means "similar to." (In everyday spoken language, people use "like" as the default now - but that's grammatically incorrect.) Eliminate B and E. (B also has a pronoun error - "it" refers to a plural noun.)

C messes up the contrast I want to make by starting with "if these fertilizers." Also generally kind of awkward / wordy, but only use that as a tiebreak.

The problem with D lies at the end of the choice: "while if substituted for more traditional fertilizers, this substitution..." Notice the first part of that, before the comma - it never actually mentions what is being substituted, either via a noun or pronoun. This is a modifying clause. The modifier is meant to modify "synthetic fertilizers" which is a noun, so this is a noun modifier - and noun modifiers must touch the noun they modify. But "this substitution" follows the comma, not "synthetic fertilizers" (or some other noun or pronoun that refers to synthetic fertilizers). No good. Eliminate D.

Which leaves us with A. Notice that A doesn't sound particularly good. But there's nothing grammatically wrong with it... It's not uncommon for A to sound not-so-good when it is the right answer - otherwise, how would they get someone to cross off A when it's right, especially on a hard question?