I didn't quite get your explanation for A: you said "passing" is a dangling modifier. In order for "passing" to be a dangling modifier it has to act as an adverb----->thus, we need an agent to do the action of passing. However, in A it's a noun and the object of "to".
I think "allowing" doesn't have a clear agent, since "the proliferation" is acting as the agent of "allowing"
well ... it's a subtle difference; when construction like that are used as gerunds in this kind of sentence, they are normally preceded by "the".however
, the gmat does not explicitly test differences in the use of articles (a, an, the), so there will be other means of elimination.
in this case, notice that "passing" is contrasted with the dedicated noun form "passage".if you see a split between
* an -ING form that's used as a noun, and
* a dedicated noun form of the same action,
then ALWAYS pick the dedicated noun form.
notice that this doesn’t mean that you should automatically reject all -ING forms of those actions, since some of them are not gerunds; some of them are modifiers, in which case you should absolutely use the -ING form.The performing of certain dance moves requires years of practice.
--> inferior, though not technically incorrectThe performance of certain dance moves requires years of practice.
--> superiorEvery year, the running of the Boston Marathon attracts hundreds of thousands of spectators.
--> this is correct, since there is no dedicated noun form (like "runnage" or "runnation").People running the boston marathon are generally in very good physical shape.
--> also correct, since the -ING form in this instance is a modifier, not a noun.