+1 for C.

A. an essential key in

B. an essential key for

C. essential for --> Correct, 'essential for' and not 'essential in'
e.g. :
A good strategy is essential for GMAT. Correct
A good strategy is essential in GMAT. Incorrect

D. essential in

E. essential

Hence, C.
_________________

Key itself means essential. Therefore, essential key is redundant. A and B are gone. The correct idiom is 'essential for.' Therefore D and E are gone. C is the correct
_________________

Essential for is correct Idiomatic usage, with (C) as well.
_________________

OFFICIAL EXPLANATION

Essential for not essential in
The original sentence contains the redundant phrase "essential key" where
"essential" would suffice. In addition, the phrase "essential . . . in the survival" is
unidiomatic. The proper idiom is "essential for the survival."
(A) This choice is incorrect as it repeats the original sentence.
(B) This choice correctly uses the idiom "essential . . .for the survival." However, the
phrase "essential key" is redundant; something "key" is by definition "essential".
(C) CORRECT. This choice replaces the redundant phrase "an essential key" with the
more concise "is essential." In addition, the idiom "essential . . .for the survival"
replaces the unidiomatic "essential . . . in the survival."
(D) This choice replaces the redundant phrase "an essential key" with the more
concise "is essential." However, it uses the unidiomatic "essential in the survival"
instead of the idiomatic "essential for the survival."
(E) This choice replaces the redundant phrase "an essential key" with the more
concise "is essential." However, the phrase "is essential the survival" is nonsensical
without a connecting preposition between "essential" and "the survival."
_________________

A. an essential key in

B. an essential key for

C. essential for

D. essential in

E. essential

IMO C
_________________

Federal government financing is an essential key in the survival of the interstate rail system.



key and essential mean same. A & B out on the basis of redundancy.


Replacement of this phrase in place of the underlined word makes the sentence nonsensical. E is out.


Between D & E
Essential for is correct idiom usage. Thus D is out too
Hence C is the winner

"essential for" is the correct idiomatic usage.

Answer: C

Federal government financing is an essential key in the survival of the interstate rail system.

The correct idiomatic structure for essential is 'essential....for...'

A. an essential key in

(A) uses the wrong idiomatic structure. Hence, (A) is incorrect.

B. an essential key for

I was confused between B and C. I picked C based on intuition, without truly understanding why B is wrong. After going through a similar comment, I realized that there's a redundancy error in (B).

essential itself means 'key'. So, there's no need to restate 'key' as is done in this option. Hence, eliminate (B)

C. essential for

Uses the right idiomatic structure. Hence, (C) is the correct answer.

D. essential in

Wrong idiomatic structure in (D). Hence, eliminate (D).


E. essential

if you plug back E in the underlined portion, the sentence you get will be:

Federal government financing is essential the survival of the interstate rail system.

By reading this sentence alone, you might get a sense of something that's missing here. Additionally, it does not have the right idiomatic structure. Hence, Eliminate (E)

Hello from the GMAT Club VerbalBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
_________________