Appearing to be the only candidate whose views would be acceptable to its membership, the Youth Canorous finally endorsed Gorge for city council.
A) Appearing to be
B) Seeming to be
C) Because he appeared to be
D) Because he seemed
E) Being

Some thoughts:
1. Opening modifier (OM):
OM modifies the subject after comma. The Youth Canorous can not become candidate. So, A, B, and E are out.
2. Before NOUN and Participle, we should use to be:
He seemed to be a hawker.
He seemed a hawker. {Not correct}
=> This eliminates D.
Answer: C
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at first glance E seems to be the correct answer but if you read the sentence carefully you will find, being is not correct as it is modifying the George and not the Youth Canorous.

I agree with you.
D seems to mean the same as C, but less wordy. However, OA is C...
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IMO, it is C

A, B, and c make the first clause (...the only candidate...) a modifier which modifies "the Youth Canorous". The moidfier should modifer George, not the Youth Canorous.

D is not a correct idiom..

+1 C

Once I read that only you can use "being" in GMAT when you can replace it with the phrase "in the process of being". Otherwise, being is wrong.

I think I deserve kudos
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Prateek176 - the issue comes down to the pronouns he and its. We have to reason backwards a bit.

That is, from the non-underlined part of the sentence we know that Gorge is the political candidate. Gorge cannot be an it.

We also have the pronoun "its," which needs a referent. That referent cannot be the Gorge the human candidate. The Youth Canorous is the only other possibile referent for "its."

Its as a possessive pronoun implies it as a personal pronoun. The Y.C. is the "it."

C and D contain the personal pronoun "he."

In addition, from context, the Youth Canorous is almost certainly a group.

How do we know that THE Youth Canorous is a group (or organization or the like)?

First, the word "the" indicates the title of a group or organization, not a proper name of a person. In English, proper names of average persons do not contain the word "the" (stage names such as Chance The Rapper or The Notorious B.I.G. don't count as proper names).

There are names such as "the Chairperson," or "the Pope." But we have only two contenders that are referents for the pronouns. One of them, Gorge, is a person running for political office. That person is a he.

The other noun has a name that is not known as a person.

Second, elaborating on the analysis above, the possessive pronoun "its" MUST refer to some noun, and cannot refer to the human political candidate Gorge. "Its" must refer to the Youth Canorous, which is therefore an "it," not a "he" per C and D.

Third, "membership" is a cue that the Youth Canorous is a group. That is, "acceptable to its membership" means "acceptable to the members of _____." People cannot be members of a "he."

Sometimes rearranging the sentence helps.

The Youth Canorous finally endorsed GORGE for city council . . . ___ seemed or appeared to be the only candidate whose views would be acceptable to ITS membership.

In the part of the original sentence that is not underlined, Gorge is the candidate who gets endorsed. A candidate cannot be an "it."

In addition, we have "its" membership. Its implies it and both can go only with the remaining pertinent noun: the Y.C. "Its" turns out to be the strongest reason that the Y.C. cannot be a "he" per C and D.

I wonder whether unfamiliar names confused you? As you can see from the stats, this question is hard. (The referent "Gorge" is far away from the pronoun AND the pronoun precedes the noun. Those two qualities are both okay in SC, but they make sentence correction more difficult.)

Hope that helps.
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Could someone advise if this strategy can be used to id the correct answers, especially in cases where the sentence opens with a because or similar.
In this question I'm dividing the sentence into:
Situation, Decision.
Therefore I came to the answer C as this made more sense:
Certain decision was made because of the Situation:
"The Youth Canorous finally endorsed Gorge for city council because he appeared to be the only candidate whose views would be acceptable to its membership."
This logically completes the sentence for the reader IMO, hence- C is the most sensible and satisfies the pronoun reference.

Please do advise whether this is a valid strategy or not.

This sentence reverses the typical order of an English sentence.

Respond in kind: change the order.

The Youth Canorous finally endorsed Gorge for city council _________
the only candidate whose views would be acceptable to its membership.

SUBJECT: Youth Canorous
VERB: endorsed
DIRECT OBJECT of verb: Gorge
The rest of the sentence describes WHY the Y.C. endorsed Gorge.
"WHY" questions are answered with "because" or a synonym for "because."

The rest of the sentence is a subordinate clause.
We need a subordinating conjunction (as, because, since) OR a relative pronoun (who) to connect the clause to the main clause.

• (A) The Youth Canorous finally endorsed Gorge for city council appearing to be
the only candidate whose views would be acceptable to its membership.
"Appearing to be" is a noun modifier, not a connecting phrase.
The phrase does not establish a "causal" logical connection.

• (B) The Youth Canorous finally endorsed Gorge for city council seeming to be the only candidate whose views would be acceptable to its membership.
"seeming to be" is a noun phrase, just like the one in A. Utterly nonsensical in meaning. No causal logic.

• (C) The Youth Canorous finally endorsed Gorge for city council because he appeared to be the only candidate whose views would be acceptable to its membership.

• (D) The Youth Canorous finally endorsed Gorge for city council because he seemed the only candidate whose views would be acceptable to its membership.
"Seemed to be" is required for this particular construction. "Seems to be" can be suspect, but "seem" as a linking (copular) verb cannot take a specifying predicate.

(E) The Youth Canorous finally endorsed Gorge for city council being the only candidate whose views would be acceptable to its membership.
being is noun modifier, not a connector. Logical nonsense.

taniad reminded me that I had not seen a very effective technique used in this instance of a "reversed" sentence.

If in doubt about logical causation, cause and effect, or whatever other name you have learned for "causality,"
rearrange the sentence as above.

Answer C
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hi Prateek176 if after super instructive explanation by generis, you are still having hard time understanding why D is incorrect,
that means you lack a basic English vocabulary but dont get desperate, check this video

www.youtube.com/watch?v=SsIHrCeH1Bc&t=13s