GMAT prep suggests that "the singular number is not idiomatic." The MGMAT guide 5th edition suggests that "THE numbers of dogs HAVE fallen" is wrong, in favor of "THE number of dogs HAS fallen." But here we have, "THEIR numbers HAVE declined," which is equival...

Well noticed. However, there are a few considerations here. First, don't trust the official explanations; they're not written by the writers of the questions and they are full of inconsistencies. But, in any case, the explanation refers to the meaning of the sentence, and that's an important thing ...

This is related to GMAT prep explanations for multiple questions. For example, something like "the machines rode around and took pictures, which were helpful in determining the quality of the sample." GMAT prep explanations keep emphasizing that "which" is ambiguous in these case...

Thanks Stacey! I found this very useful myself.

I am referring to the OG questions in Wiley.

In this post https://www.manhattanprep.com/gmat/forums/medical-researchers-at-harvard-and-stanford-t30344.html , Ron writes no. you can only use 'comma + __ing' if the __ing part is inseparable from whatever is described in the main clause. e.g., Joseph was struck by a cab, dying ins...