Drinking coffee may significantly reduce the risk of cirrhosis of the

teaserbae , this question is harder than it appears.

The sentence intends to convey that the consumption of coffee may do two equally important things:
1) reduce risk (of contracting cirrhosis of the liver), and
2) aid (help) sufferers (of migraine headaches)

The biggest issue in all four incorrect answers is lack of parallelism, which in A, B, and D creates nonsensical meaning.

In A, B, and D, however, first we have to recognize that "aid" is used as a noun, a task that may be hard for non-native speakers.

SPLIT #1: "Easy" parallelism error
Incorrect: VERB and VERB-ING
(E) reduce . . . [as well as] aidING are not parallel

Eliminate (E)

Split #2: Parallelism error that is harder to spot: VERB/verb phrase and NOUN (phrase)

When aid is a noun: AID TO and AID FOR are correct. Both are idiomatic noun phrases.

In fact, those constructions signal that aid IS a noun.

We cannot use AID FOR or AID TO when aid is a verb
If you see AID FOR or AID TO, those phrases signal that AID is NOT a verb, but rather a noun (in a noun phrase)

Split #2, continued: Parallelism that may be hard to spot
VERB/VERB PHRASE ... NOUN (phrase)
are not parallel

(A) reduce ... and also aid for
-- FOR signals that aid is a noun
-- reduce (verb) ... and also aid (noun) for
-- VERB ... NOUN (phrase) => not parallel

P.S. whatever may have been the case previously,
"and also" is not automatically wrong on the GMAT unless the construction at issue is "both . . . and.".
Allowed: X and also Y. My neighbor mowed her lawn and also cleaned her porch.
Not allowed: Both X and also Y. My neighbor both mowed her lawn and also cleaned her porch.
If we have no other basis upon which to decide between two answers, choose the one that uses only "and" rather than the one that uses "and also."
Otherwise, find a different error. Correct official questions have used "and also."

(B) be significant in reducing ... and aid for
-- VERB PHRASE ... NOUN (phrase)
-- Same as (A)

D) cause ... and aid to
-- TO signals that aid is a noun
-- VERB ... NOUN (phrase)
-- Same as (A)
AID TO is similar to AID FOR.
The idiomatic construction "aid to" signals that AID is part of a noun phrase and is NOT a verb, just as "aid for" does.

Eliminate A, B, and D

Split #2a: Illogical and nonsensical meaning

Because A, B, and E use AID as a noun, they create a deceptive parallel between the noun RISK and the noun AID.
As a result, the sentences proclaim that drinking coffee may reduce both risk and aid.
Huh? May reduce aid?
How might drinking coffee reduce HELP?

Eliminate A, B, and D

By POE, Answer (C) is correct

Analysis of (C): Drinking coffee may significantly reduce the risk of cirrhosis of the liver and aid sufferers of migraine headaches ...

• The verbs reduce and aid are parallel
• The verb "aid" correctly is not followed by the prepositions TO or FOR
• Subject + aid + direct object construction is correct

In this case, aid is a transitive verb that requires a direct object (sufferers), which receives the action of the verb without being interrupted by TO or FOR.
The construction is correct.

ANSWER C

I hope that helps.

AID as an idiom

NOUN
• Allowed: AID TO
aid to developing countries

• Allowed: AID FOR
aid for victims of the civil war

• Allowed: AID IN _____ ing
aid in finding a solution

• INCORRECT: AID + infinitive

When aid is a noun, AID cannot be followed by an infinitive. Ever.

Incorrect: Her aid to fix the problem was essential.
Correct: Her aid in fixing the problem was essential.

VERB

• Allowed: Subject + aid + direct object

She aided the wounded people.
He aided a friend.

• Allowed: Subject + aid + "in ______ING" [IN + gerund VERB-ING]

She aided in comforting the wounded people.
(the "in ___ ING" phrase is okay because it describes the activity or event in which she is helping)

He aided in catching the criminal.

• Not allowed: When aid is a VERB it CANNOT be followed by FOR or TO

INCORRECT: She aided to the wounded people.
INCORRECT: She aided for the wounded people.
INCORRECT: She aided to comforting the wounded people.

*In this OG question, the last two options are incorrect because they are constructed this way:
• the goddess Bona Dea's aid TO HELP
• "to help" is an infinitive (not okay!). The correct answer has this construction: aid in helping