All of the carbon-emissions permits were supposed to be sold at auction, but the bill's authors ended up giving away 85 percent of them free at the outset of the program, which won votes, but that some environmental advocates said undercut the program's integrity.
A. program, which won votes, but that some environmental advocates said
B. program, thereby winning votes; however, some environmental advocates said this
C. program that won votes but that some environmental advocates said
D. program to win votes, however this was said by some environmental advocates to
E. program, and it won votes, of which some environmental advocates said
"This" has no referrent in most of the options and by the way, Gmat doesn't likes "this". In E, what is "it" referring to? "it" will always standby for the noun but here it stands for "ended up giving away 85 percent of them". Thats incorrect.
In D, the meaning has entirely changed by using infinitive construction, implying an "intention".
In A, which modifies "program". It was NOT the program that won votes.
Logically speaking, since "but that" is being used, therefore a "that" phrase is needed for parallelism.
Hope that helps.
P.S. Always do mention the source of the question. It helps us to know the credibility of the question.
Prepositional Phrases Clarified|Elimination of BEING| Absolute Phrases Clarified
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