Sentence Correction

Received a PM asking me to respond. I don't see the author listed for this problem. If you'd like my take, please cite the author and then I'll be happy to add my 2 cents!

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.

C: the official explanation would probably say something like "the slowness of the growth of" is awkward. It's also the case that "slowness" changes the original meaning. The original meaning is about slowing growth - think, there's a certain growth rate, and that rate is declining over time.

"Slowness of the growth" just means something is slow to grow in general. It doesn't mean that the rate of growth is declining over time.