C is an appositive too. The presence of absence of "that" after "phenomenon" doesn't change that basic structure. Notice that what follows the "that" in C is _not_ a "noun clause" (or as I'd prefer to call it, a content clause), because there's a relativized element. Here's the structure (gap marked):

a phenomenon [{Rel Cl} that most scientists agree [{Content Cl.} [that] ___ is caused by human beings' burning of fossil fuels]]

Notice that this clause in turn contains its own subordinate clause, and this one actually is a content clause. The relativized element is the subject of that inner content clause. If you're having trouble seeing the relationships, try pulling apart the sentence into its components by "unrelativizing" things:

[the] phenomenon is caused by human beings' burning of fossil fuels ->

most scientists agree [that] [the] phenomenon is caused by human beings' burning of fossil fuels

There are two sites, one at the start of the relative clause, the other at the start of the content clause, where "that" can appear, but need not. The fact that A and C differ in their use of "that" is window-dressing for the problem that has nothing to do with the grammaticality of either choice.

I'm with the others who think that C is best and that A is not idiomatic. It's also worth noting that C observes a fussy prescriptive rule: genitive case for the "subjects" of gerunds. Such rules are never directly tested on the GMAT or other standardized tests of English writing, but the item writers do largely observe them in their correct answers, and so they can be a signal as to what is supposed to be correct.

Regards,

Karl

On 2/26/2018 3:13 PM, Geoffrey Layton wrote:
[log in to unmask]">

C" seems to want to try to turn the construction into a noun clause, which doesn't work nearly as well as the appositive. Since "A" is the only choice that is an appositive, "A" is the correct answer. 



From: Assembly for the Teaching of English Grammar <[log in to unmask]> on behalf of Linda Di Desidero <[log in to unmask]>
Sent: Monday, February 26, 2018 4:33 PM
To: [log in to unmask]
Subject: Re: GMAT Question
 
I actually like A!

On Mon, Feb 26, 2018 at 4:21 PM, Dick Veit <[log in to unmask]> wrote:
B is ungrammatical ("agree that is caused...").
The "in burning fossil fuels" in A and in the original is unidiomatic.
D and E are more convoluted than necessary, though grammatical.
C is the the most natural choice for me.
This also would be good:  a phenomenon that most scientists agree is caused by human beings burning fossil fuels,

On Mon, Feb 26, 2018 at 3:56 PM, Jessica Thomasson <[log in to unmask]> wrote:
Answer C sounds most natural to me.

Virus-free. www.avast.com

On Mon, Feb 26, 2018 at 3:53 PM, John Crow <[log in to unmask]> wrote:
A former student of mine is studying for the GMAT and is struggling with the sentence structure section.  She sent me a sample from the practice test.  Not only did I miss it, but I disagree with the answer that was given.  What is your take?

The World Wildlife Fund has declared that global warming, a phenomenon most scientists agree to be caused by human beings in burning fossil fuels,will create havoc among migratory birds by altering the environment 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 a phenomenon caused by human beings who burn fossil fuels, E. which most scientists agree to be a phenomenon caused by fossil fuels burned by human beings,
To join or leave this LISTSERV list, please visit the list's web interface at: http://listserv.muohio.edu/archives/ateg.html and select "Join or leave the list"

Visit ATEG's web site at http://ateg.org/



To join or leave this LISTSERV list, please visit the list's web interface at: http://listserv.muohio.edu/archives/ateg.html and select "Join or leave the list"

Visit ATEG's web site at http://ateg.org/



To join or leave this LISTSERV list, please visit the list's web interface at: http://listserv.muohio.edu/archives/ateg.html and select "Join or leave the list"

Visit ATEG's web site at http://ateg.org/



To join or leave this LISTSERV list, please visit the list's web interface at: http://listserv.muohio.edu/archives/ateg.html and select "Join or leave the list"

Visit ATEG's web site at http://ateg.org/


To join or leave this LISTSERV list, please visit the list's web interface at: http://listserv.muohio.edu/archives/ateg.html and select "Join or leave the list"

Visit ATEG's web site at http://ateg.org/


To join or leave this LISTSERV list, please visit the list's web interface at: http://listserv.muohio.edu/archives/ateg.html and select "Join or leave the list"

Visit ATEG's web site at http://ateg.org/