Stacey Koprince wrote:Oh, I see how they explained it. Yes, you could read it that way too (and, grammatically, you have to, actually), because "damaged" and "slowed" are parallel.

I was reading it based upon what I knew the meaning should be, logically. The original sentence is trying to discuss two possible effects of acid rain: slowing the growth of forests and damaging those same forests.

D says:
what role is played by acid rain in [damaged or slowed] growth of forests.

or = parallelism signal
the two -ed words are parallel and function as adjectives; they apply equally to the next noun (growth):
what role is played by acid rain in damaged growth
what role is played by acid rain in slowed growth

Now, because of the parallelism, I have "damaged growth" but the original sentence didn't say the growth was damaged. It just said the forests were damaged. (Well, potentially damaged - that's the debate, of course.)

(Note: and if you wanted to read it as "damaged" applies to forests, then you'd have "what role is played by acid rain in damaged forests" - which is also wrong, as I noted before. Either way, it's wrong. )

In E, we've got:
what role is played by acid rain in [damaging or slowing the growth of] forests.

or = parallelism signal
the two -ed words are parallel and function as nouns this time (gerunds); they each apply equally to the rest of the sentence:
what role is played by acid rain in damaging forests
what role is played by acid rain in slowing <the growth of> forests

Now, you're actually describing the actions potentially taking place: damaging and slowing. "the growth of" is just extra modifying info. Slowing what? Slowing the growth.

Stacey Koprince wrote:I think I understand what you're saying. Yes, you could interpret it as "damaged forests" and "slowed growth of forests" - but then you still have a meaning problem. What role acid rain plays in damaged forests - that makes it sound like the forests were already damaged by something else, before the acid rain came along. That's not the intention - the intention is to say that the acid rain is (potentially) causing damage - or damaging the forests.

Stacey Koprince wrote: "damaging or slowing the growth of forests" - now, the word "the" in front of growth means "the growth of" can now just be additional words applying to the main -ing word "slowing." So, both -ing words are now free to apply to "forests."