A middleweight black hole weighs in at roughly 500 solar masses, hundreds of times more massive than the lightweight black holes produced by the collapse of individual stars, but thousands or even millions of times less in its mass as the heavyweight giants that lurk in the centers of galaxies.

(A) thousands or even millions of times less in its mass as
(B) it is thousands or even millions of times less massive as
(C) thousands or even millions of times less massive than
(D) yet it is thousands or even millions times less massive than
(E) yet it is thousands or even millions of times less in its mass than

Source: GMATPrep test2; OA is C
I can pick up the right option, but there 3 things making me confused:

1# the phrase in red color is a modifier that modifies 500 solar masses or A middleweight black hole, which one dose the phrase modify?(i think that, if a modifer such as adj phrase is intended to modify the subject,there should not be a Noun or Object before the modifier to avoid ambiguity.)

2# When writting A, B, and C, we need two comma, but when writting A and B, we don't need comma. In Option (C), 'A'--hundreds of times more massive than the lightweight black holes produced by the collapse of individual stars , but 'B'--thousands or even millions of times less massive than the heavyweight giants that lurk in the centers of galaxies dose consist of a comma. why? could explain the context in which we need a comma in A, and/but B?(this issue is a tricky one since we know there should be a subclause when but/and follow a comma.)

3# i have nerver seen the usage of less in its mass,or in its number,height, and volume ; regardless the special context of this quetion, could such usage be gramatically ok? if so, could you provide an example?

I came across this question today in GMAT prep and choose D.

Instructors any thoughts why C is correct as "comma + but" should follow an independent clause.

Although I understand but and yet seem to be redundant, I cannot reason out C.

Thanks.

3 things.

1 -- MOST IMPORTANT
PUNCTUATION IS NOT TESTED! DO NOT WORRY ABOUT PUNCTUATION!
ahem.

2 --
in choice (c) the commas are a non-issue anyway; they belong to the modifier, not to the overall structure of the sentence. (try removing the modifier; you should be able to write the remaining sentence without that comma.)

3 --
among the main reasons why punctuation isn't tested is that it is inconsistent. in particular, longer sentences tend to use more punctuation, and shorter sentences tend to use less.

for instance,
i tried hard but failed
i tried hard, but failed
both acceptable; the difference is mostly rhetorical (and 100 percent outside the domain of the gmat).

i tried as hard as i could until i was totally exhausted, but failed anyway
--> this one pretty much has to be written with the comma, because without the comma it's essentially unreadable. (take out the comma and see how weird it becomes.)

most importantly, though, refer to #1 above.

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