The rapid-rail lines that were recently introduced in

Question

The rapid-rail lines that were recently introduced in southern California have had positive effects:  not only have they lowered pollution levels, they have helped in decongesting  the region's freeway system, which had been operating far above its capacity.

A. not only have they lowered pollution levels, they have helped in decongesting
B. the lines have not only lowered pollution levels, but also helped to decongest
C. not only have pollution levels been lowered, but they have helped to decongest
D. lines have lowered pollution levels, as well as helped in decongesting
E. not only have they lowered pollution levels, but also have they helped decongest

agdimple333 · Answer

B.

A, C are out because of incorrect use of idiom. D changes the meaning.
of B and E, B is better. In E, 'also have they helped' is awkward construction.

crick20002002 · Answer

This is a tough one.

B would have been an easy choice if "helped to decongest" were replaced by "helped in decongesting".

A does not look correct because of ambiguous "they": does it refer to rail-lines or to positive effects.

So i am left with D.

Crick

mayansd · Answer

B for me.

A and C are out, as idiom "not only..but also" is not followed. E is awkward. Left with B and D. I will go with B, as " the  lines" in B clearly refer to the lines mentioned previously in the sentence, whereas in D it is just "lines", which can be ambiguous.

OA??

sudhir18n · Answer

Can any one explain how is 
not only  lowered pollution levels  parallel to  but also helped to decongest

Warlock007 · Answer

hey sudhir though its quite weird to help you (as you had 0 incorrect in MGMAT) :wink:

but still here is my view on this not only lowered .......xxxxxx || but also helped ..............xxxxx now xxxxx could be anything we need not to consider its role in the sentence for us lowered should be "parallel" to "helped"

forget what is ahead in the sentence

WishMasterUA · Answer

I choose B.
My explanations are below

sudhir18n · Answer

Can you explain howz that the correct idiom?
Not only X but also Y., both X and Y must be parallel .. are they?
I dont think so they are in B.

WishMasterUA · Answer

I think they are.

the lines have  not only lowered   something ,  but also helped   in something

bschool83 · Answer

Crick,

This is a straight B.

'To help' is a special verb form that can be followed either by a bare infinitive or by a to-form infinitive. It is rarely used in the form Verb + Preposition + gerund. There are very few verbs that are followed by a preposition and a gerund. GMAT almost always prefers the to-form infinitives over the gerund-form.

This is the order GMAT usually prefers in order of correctness:
I helped to raise angel capital >> I helped raise angel capital >> I helped in raising angel capital

Hence, if "helped to decongest" were replaced "with" "helped in decongesting", it would be an incorrect answer choice.

Also a small thing (unrelated to question), the correct idiom usage of replace is 'to replace with' and not 'to replace by'.

Hope it helps.

RivaM · Answer

B has correct idiom usage and also its a stand alone sentence unlike D which misses "The" infront of lines.

crick20002002 · Answer

Thanks a lot for the explanation !! +1 Kudos !!

Crick

The rapid-rail lines that were recently introduced in

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