The questions that test Idiomatic usage are always tricky since if a test-taker is not aware of the idiom he or she can end up spending a lot of time trying to sort out other errors and might be going back and forth between options that are idiomatically incorrect.

While it would be easy to give a long list of idioms to learn by rote, a list does not really serve any purpose since the list can become vast and cumbersome and there is no guarantee that you will able to retrieve this idiom from memory when you encounter it.

A better way would be to scour the OG and look at the idioms that are consistently tested on the GMAT Sentence Correction. 

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IDIOM 1: HYPOTHESIS/HYPOTHESISE THAT

The word hypothesis means an argument/assertion/contention/claim that has not been proven go be correct yet. The verb for of the same would be similar to argue/assert/contend/claim.

From this it is clear that just like the words ARGUMENT and ARGUE have to followed by THAT,

• The argument THAT it is too early to increase interest rates is….
• The governor argued THAT it is too early to increase interest rates…

HYPOTHESIS and HYPOTHESISE have to followed by THAT, which is the error tested in the GMAT Sentence Below.

SENTENCE #1

Gall’s hypothesis of there being different mental functions localized in different parts of the brain is widely accepted today.

(A) of there being different mental functions localized in different parts of the brain is widely accepted today

(B) of different mental functions that are localized in different parts of the brain is widely accepted today

(C) that different mental functions are localized in different parts of the brain is widely accepted today

(D) which is that there are different mental functions localized in different parts of the brain is widely accepted today

(E) which is widely accepted today is that there are different mental functions localized in different parts of the brain

The sentence surprisingly is testing only the one error related to the usage of the word hypothesis. The only option in which it is rightly used is Option C.

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IDIOM 2: CONSIDERED not CONSIDERED AS

The word CONSIDERED should never be followed by AS, since the meaning of the word is THINK OF AS or REGARD AS. So using an AS after CONSIDER is redundant.

SENTENCE #2

George Sand (Aurore Lucile Dupin) was one of the first European writers to consider the rural poor to be legitimate subjects for literature and portray these with sympathy and respect in her novels.

(A) to be legitimate subjects for literature and portray these

(B) should be legitimate subjects for literature and portray these

(C) as being legitimate subjects for literature and portraying them

(D) as if they were legitimate subjects for literature and portray them

(E) legitimate subjects for literature and to portray them

CONSIDER need not be followed by to be or should be, it can straightaway be followed by legitimate, making all options except E incorrect.

The first option might seem correct to the ear — consider to be. A small example can highlight the redundancy in using to be:

• I consider him to be my rival ×
  • I consider him my rival
• I consider him to be a worthy successor to my throne ×
  • I consider him a worthy successor to my throne.

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IDIOM 3: ABILITY TO (not OF) and CAPABLE OF (not TO)

The word ABILITY is always used in conjunction with TO — the ability to do something— and the word capable is always used in conjunction with OF — he is now capable of playing for a longer duration.

This GMAT Sentence Correction questions tests all the idioms we have covered so far in a single sentence.

The results of two recent unrelated studies support the idea that dolphins may share certain cognitive abilities with humans and great apes; the studies indicate dolphins as capable of recognizing themselves in mirrors—an ability that is often considered a sign of self-awareness—and to grasp spontaneously the mood or intention of humans.

(A) dolphins as capable of recognizing themselves in mirrors—an ability that is often considered a sign of self-awareness—and to grasp spontaneously

(B) dolphins’ ability to recognize themselves in mirrors—an ability that is often considered as a sign of self-awareness—and of spontaneously grasping

(C) dolphins to be capable of recognizing themselves in mirrors—an ability that is often considered a sign of self-awareness—and to grasp spontaneously

(D) that dolphins have the ability of recognizing themselves in mirrors—an ability that is often considered as a sign of self-awareness—and spontaneously grasping

(E) that dolphins are capable of recognizing themselves in mirrors—an ability that is often considered a sign of self-awareness—and of spontaneously grasping

B & D can be eliminated straightaway because they use CONSIDERED AS instead of CONSIDERED; D can also be eliminated for the incorrect usage — ABILITY OF.

A, C & E use the structure

• CAPABLE OF X (followed by additional information about X) AND…

The correct structure should be parallel — CAPABLE OF X and OF Y, which is only followed in E.

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More idioms in the forthcoming Sentence Correction posts.