Since the 1930s aircraft manufacturers have tried to build airplanes

himanshu0077

No, there's no rule that comma + -ed makes an action modifier. That's one option, but it's also very common to see this construction used for noun modifiers. Certainly, we want to try to choose an interpretation that works, and this one is a bit too far-fetched. We can more reasonably apply the modifier to "wings." One could argue that we have a bit of ambiguity here--perhaps the modifier applies to "airplanes"?--but since the adverbial version doesn't create a logical meaning, we should treat this as a noun modifier.

In the Official Guide, the main reason used to get to B is that we want to say that the wings themselves are smooth, not that the process of shaping them was done smoothly. This is an interesting result for 2 reasons:
1) It's a good reminder that "this changes the meaning" is not a good criterion for eliminating an answer. B is actually the only choice that says the wings themselves are smooth, and it's the right answer!
2) The parallelism is not simple. A hard question is often going to press us to do more than just get our parallel words in the same form (smooth and perfect, smoothly and perfectly). In fact, if we see that some of the answers have a simple structure like that, while others separate out the terms ("so smooth" and "so perfectly shaped"), it's worth considering that that additional complexity is needed to fix a problem.

Here are a couple of official examples that illustrate my point # 2):

https://gmatclub.com/forum/the-first-tr ... ml#p235977
https://gmatclub.com/forum/downzoning-z ... 85884.html