When the temperature of a gas is increased, it is either

[Anne1276]

GMAT Prep Practice CAT

When the temperature of a gas is increased, it is either accompanied by an increase in pressure if the gas is enclosed in a container, or an increase in volume if the gas is able to expand.

A) Same
B) When the temperature of a gas is increased, it is accompanied either by an increase in pressure if it is enclosed in a container or
C) When the temperature of a gas is increased, the increase is either accompanied by an increase in pressure if the gas is enclosed in a container or by
D) Any increase in the temperature of a gas is either accompanied by an increase in pressure if it is enclosed in a container or by
E) Any increase in the temperature of a gas is accompanied either by an increase in pressure if the gas is enclosed in a container or by

I chose C. The correct answer is E. Could somebody please explain the difference between the "openers" of those sentences - how do I know when to use "Any increase in . . . " vs. "When blah, blah". Also, does this have anything to do with the placement of the word "either"?

Thanks.

[StaceyKoprince]

The two main issues here are pronouns and idioms - you could construct a grammatically correct sentence with either the "when" opener of the "any" opener. This is what I call a "red herring" - an obvious difference in the answer choices, so you agonize over that when you should be focused on something else.

In the original sentence, the pronoun "it" is ambiguous - does "it" refer to the temperature or the gas? Technically it could be either one (although I know it should be referring to temperature just because I've learned about this stuff before).

The next big issue with this one is the lack of parallelism within the idiom "either X or Y." The original sentence says "it is either accompanied by... or an increase..." With these kinds of idioms, you have to be able to write both X and Y as though they are the sole enders of the sentence. So I need to be able to write complete sentences by saying "it is accompanied by..." (which is okay here) and "it is an increase in..." (which is not okay).

B has the same pronoun issue and also messes up the "accompanied by" idiom - it needs to say "accompanied either by X or by Y."

C (awkwardly) eliminates the pronoun issue but still messes up that idiom.

D eliminates the pronoun issue but still messes up that idiom.

E fixes both the pronoun ambiguity and the idiom error.

[Anon]

Hi..

Is there a trick to spot inverted sentences...
I thought the above is an inverted sentence...but not sure... could you please verify

further..in E

"Any increase in temperature of a gas IS..."

Could you please clarify what is the main subject and predicate here... as I am getting lost because of the preposition and its object...

thanks in advance,
Anon

[StaceyKoprince]

Core of the sentence: Any increase is accompanied either by X or by Y

"in the temperature" and "of a gas" are both prepositional phrases. But "any" is not a preposition. Any is a quantity word or qualifier and can be used to introduce the noun (subject in this case) increase. In terms of part of speech, it's equvalent to saying "an increase is..." or "the increase is..."

It is very tough to spot inverted sentences. The two most obvious markers are the words "here" or "there" followed by a verb. The words "here" and "there" don't function as subjects. Having only prepositional phrases before the verb is also another clue - so it's good that you were looking for that. It just turns out that we had something else besides prepositional phrases here... and that was the subject, of course.

[Anon]

Thanks a ton for the explanation Stacey.. :)

Anon

[rfernandez]

We're glad it helped!

[aaa]

How does c "mess up" the idiom?

[RonPurewal]

How does c "mess up" the idiom?

it's actually an issue of parallelism, not idiomatic usage. remember that two-part parallel constructions (such as "either ... or ...") must be exactly parallel grammatically.

choice c has the following structure:
[i]the increase is either accompanied by an increase in pressure if the gas is enclosed in a container or by an increase in volume of the gas...

that's not parallel, because the first part starts with "accompanied by", and the second part starts with just "by".

EDITED: (hat tip to user "joebob")
if you put "accompanied" BEFORE "either", then the second part SHOULD start with "by", because in that case the first part would start with "by".

[joebob]

Ron,

If I am interpreting the last part of your post correctly, then this is correct: "The increase is accompanied either by an increase in pressure or an increase in volume" AND this is incorrect: "The increase is accompanied either by an increase in pressure or by an increase in volume." ?

How does c "mess up" the idiom?

it's actually an issue of parallelism, not idiomatic usage. remember that two-part parallel constructions (such as "either ... or ...") must be exactly parallel grammatically.

choice c has the following structure:
[i]the increase is either accompanied by an increase in pressure if the gas is enclosed in a container or by an increase in volume of the gas...

that's not parallel, because the first part starts with "accompanied by", and the second part starts with just "by".

if you put "accompanied" BEFORE "either", then the second part should NOT start with "by".

[Guest]

bump

[RonPurewal]

Ron,

If I am interpreting the last part of your post correctly, then this is correct: "The increase is accompanied either by an increase in pressure or an increase in volume" AND this is incorrect: "The increase is accompanied either by an increase in pressure or by an increase in volume." ?

How does c "mess up" the idiom?

it's actually an issue of parallelism, not idiomatic usage. remember that two-part parallel constructions (such as "either ... or ...") must be exactly parallel grammatically.

choice c has the following structure:
[i]the increase is either accompanied by an increase in pressure if the gas is enclosed in a container or by an increase in volume of the gas...

that's not parallel, because the first part starts with "accompanied by", and the second part starts with just "by".

if you put "accompanied" BEFORE "either", then the second part should NOT start with "by".

oh dear, i did screw that up, didn't i.

i have edited the original post accordingly.
hat tip for pointing this out.

[anoo_anand]

Cannot we eliminate A,B,C - beacuse they are starting with "WHEN" , when is used only when there is a time frame - refrence ?

Thanks

[RonPurewal]

Cannot we eliminate A,B,C - beacuse they are starting with "WHEN" , when is used only when there is a time frame - refrence ?

Thanks

no.

you have to be describing events that occur in overlapping time frames, but there's no need to make explicit references to the timeframes themselves.

e.g.
the sky becomes bright when the sun rises
this is definitely an ok sentence, even though it doesn't contain any explicit references to time frames.

[vivs.gupta]

the increase is either accompanied by an increase in pressure if the gas is enclosed in a container or by an increase in volume of the gas.

Hi Ron,

In the above sentence, can't we use the concept of ellipse and assume 'accompained' after 'or':

the increase is either accompanied by an increase in pressure if the gas is enclosed in a container or (accompained) by an increase in volume of the gas.

[jlucero]

the increase is either accompanied by an increase in pressure if the gas is enclosed in a container or by an increase in volume of the gas.

Hi Ron,

In the above sentence, can't we use the concept of ellipse and assume 'accompained' after 'or':

the increase is either accompanied by an increase in pressure if the gas is enclosed in a container or (accompained) by an increase in volume of the gas.

With a single parallel marker you are given some wiggle room, but not with two parallel markers.

Either X or Y

X and Y need to be completely parallel, ESPECIALLY with the initial structure of the sentence.

Either (accompanied by...) or (by...) WRONG