GMAT Sentence Correction (SC) | Re: The increase in unemployment rates, coupled with

The problem in the original is that D is trying to apply a modifier to two things, and "as well as" doesn't do what "and" does in that situation:

He was greeted by men in green shirts and hats. (The shirts and hats were both green.)
He was greeted by men in green shirts as well as hats. (This doesn't really work well at all. It probably means that the hats were not green. Or if we stretch a bit, it could mean he was greeted by men and by hats. Basically, we just don't want