OG12-sc118. The world wildlife fund has declared that global warming, a phenomenon most scientsts agree to be caused by human begings in burning fossil fuels, will create havoc among migratory birds by altering the enviroment in ways harmful to their habitats.

a) A phenomenon most scientists agree to be caused by human beings in burning fossil fuels,
b) a phenomenon most scientists agree that is caused by fossil fuels burned by human beings,
c) a phenomenon that most scientists agree is caused by human beings' burning of fossil fuels
d) which most scientists agree on as phenomenon caused by human beings who burn fossil fuels,
e) which most scientsts agree to be a phenomenon caused by fossil fuels burned by human beings

Although the answer is c, in OG12-sc24, OG said
The -ing form of a verb can be used as a noun, but it is often awkward, particularly when used with a possessive.

I just wonder what is the right form of using -ing with a possessive.

Why “B” is wrong? Is it because it is in “Passive” voice

heh. another instance in which liberal politics finds its way onto the gmat.
actually, most of the "science" purporting to show that humans cause global warming has been severely discredited, but we're not likely to see that in a test sentence anytime soon.

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according to the context of the sentence, the phenomenon is caused not by the fossil fuels themselves, but by the burning of those fuels.
so choice (b) is incorrect, because it states that the phenomenon is caused by the fuels themselves.
to prove this, note that "burned by human beings" is a modifier, and that modifiers MUST be able to be removed without affecting the essential context of the sentence.

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and yes, the OG is very annoyingly inconsistent on declaring what is "awkward" and what is not.
this is certainly not the first instance in which a construction that has been declared "awkward" on one occasion is then found in another correct answer!

luckily, we at the manhattan gmat forums have a much better grip on which usage is awkward and which is not than, ironically, the answer key to the og itself.

One thing that am confused about, how did you infer that the original meaning of the context is that global warming was caused by the burning of the fossil, especially when you have different meaning among every option. even in the original sentence it says:"by human beings in burning fossil fuels".

well, that's pretty much the only reasonable interpretation of the sentence. the global warming described in the problem has to be the result of some process -- i.e., it doesn't make sense to state that it is the result of human beings themselves -- and that's the only process described that could legitimately cause such a phenomenon.

make sure that you are aware of this:
in sentences for which there is only one reasonable meaning, that gmat will absolutely expect you to figure out that meaning, and, if necessary, to alter the structure of the sentence in order to convey that meaning.

if there are two or more reasonable meanings, then the gmat will resolve the ambiguity for you. i.e., you will not be forced to choose between two competing meanings that are both legitimate and reasonable (unless one of the sentences is grammatically incorrect).