(b) actually doesn't have correct parallelism.
the "the" in front of clearing indicates that it's a noun form. (there's no such word as clearage, or clearation, or whatever, so this is the best noun form you're going to get here.)
to be parallel to the clearing, you need another dedicated noun form. here, that's the removal.

From RON:

removal is better.
there are a bunch of words like these, with specific noun forms that, simply because they exist, are considered better than the corresponding gerund (-ing) forms. notable among this class of nouns are the '-al' forms, like removal, betrayal, etc.

unfortunately, there are no general tips of the form you're soliciting; such are the joys of the english language. the closest i can get to a general rule is this: if a special noun form exists, use it. if not, use the -ing form.
as for your examples above, you wouldn't want 'removing' because removal is a better substitute. clearing, though, is fine because there's no specially designated noun form for that one.

https://www.manhattanprep.com/gmat/forums/the-cottontail-rabbit-population-in-orange-county-t3012.html