Until scientists invented the artificial isotopes, carbon ex

Question

Until scientists invented the artificial isotopes, carbon existed in two forms - either in planar sheets of atoms, in which case it becomes a soft material and conducts electrical impulses, or  three dimensional structure, which makes it the hardest known material and acts  as an insulator.

a) three dimensional structure, which makes it the hardest known material and acts
b) in three dimensional structure, which makes carbon the hardest known material and acts
c) in three dimensional structure, in which case it becomes the hardest known material and acts
d) three dimensional structure, making it the hardest known material and acting
e) three dimensional structure and it becomes the hardest known material and acts

AMITAGARWAL2 · Answer

either in ..... it should be or in............ only B and C

C has same issue as A...   it   does not have correct antecendent.. Carbon or Structure...

minkathebest · Answer

I would go with B.

B and C have the parallelism of "in" . In C it is not clear what "it" is - structure or carbon or what have you.

adityapagadala · Answer

+1 for C...as either in X or in Y is idiomatic 
either in x, in which case...or in Y, in wioich case.

Whats thats the OA?

fameatop · Answer

Until scientists invented the artificial isotopes, carbon existed in two forms - either in planar sheets of atoms, in which case it becomes a soft material and conducts electrical impulses, or  three dimensional structure, which makes it the hardest known material and acts  as an insulator.
 Correct comparison structure is   Either X or Y  , wherein X & Y must be grammatically as well as logically parallel

a) three dimensional structure, which makes it the hardest known material and  acts  
 X & Y are not parallel because X =  IN  planar sheets of atoms; whereas Y = three dimensional structure without any preposition. Moreover use of WHICH distorts the meaning because "WHICH ACTS" means that the Structure is acting as an insulator rather than Carbon itself. Thus Incorrect

b) in three dimensional structure, which makes carbon the hardest known material and acts
 Use of WHICH distorts the meaning because "WHICH ACTS" means that the Structure is acting as an insulator rather than Carbon itself. Thus Incorrect

c)  in  three dimensional structure, in which case it becomes the hardest known material and acts
 CORRECT

d) three dimensional structure, making it the hardest known material and  acting 
 X & Y are not parallel because X =  IN  planar sheets of atoms; whereas Y = three dimensional structure without any preposition. Moreover use of ACTING distorts the meaning because "ACTING" means that the Structure is acting as an insulator rather than Carbon itself. Thus Incorrect

e) three dimensional structure  and  it becomes the hardest known material and acts
 X & Y are not parallel because X =  IN  planar sheets of atoms; whereas Y = three dimensional structure without any preposition. Use of AND without any Comma creates a run-on sentence. Thus Incorrect

blueseas · Answer

We have only 2 contenders : B and C
EITHER IN ...OR IN....==>parallel.

OPTION B is wrong because of the usage of WHICH....now WHICH in this case is refering to STRUCTURE ..but structure CANNOT make or act==>so this is wrong because meaning is illogical.

hence C wins.

fameatop · Answer

Structure  can make  Carbon the hardest known material but structure  can't act as an Insulator.

blueseas · Answer

no fameatop..

This is incorrect because three dimensional structure does not make carbon the hardest known material. It is the fact that carbon exists in three dimensional structure that makes carbon the hardest known material.

regards

bhisma · Answer

can someone clarify what  it  refers to in answer choice C ?

Until scientists invented the artificial isotopes, carbon (Singular)  existed in two forms - either in planar sheets of atoms (plural),  in which case it (Singular)  becomes a soft material and conducts electrical impulses, or three dimensional structure (Singular) , which makes  it (Singular)  the hardest known material and acts as an insulator.

a) three dimensional structure, which makes it the hardest known material and acts
b) in three dimensional structure, which makes carbon the hardest known material and acts
c) in three dimensional structure, in which case  it  becomes the hardest known material and acts 
d) three dimensional structure, making it the hardest known material and acting
e) three dimensional structure and it becomes the hardest known material and acts

blueseas · Answer

both IT are referring to CARBON .
if you think that pronoun IT is ambiguous in this sentence ..then just try to replace both the singular nouns ..and check which makes sense..
PRONOUN rule is not a definite rule and many a times accepted in GMAC questions.
please refer below article too to understand that in which all cases pronoun ambiguity is acceptable in GMAT

VerbalBot · Answer

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.

Until scientists invented the artificial isotopes, carbon ex

Prep Toolkit

Top 5 GMAT Debrief Videos

615 to 715 in 15 Days (Ria's Strategies)

More than Quant/Verbal Abilities: Speed vs. Accuracy

745 with Only Self-Prep and GMAT Club

From 555 to 765: 210-point Improvement

Perfect 805 Score Debrief by Julia

My Rewards

GMAT Sentence Correction (SC - EA only) Questions

Until scientists invented the artificial isotopes, carbon ex

Prep Toolkit

615 to 715 in 15 Days (Ria's Strategies)

More than Quant/Verbal Abilities: Speed vs. Accuracy

745 with Only Self-Prep and GMAT Club

From 555 to 765: 210-point Improvement

Perfect 805 Score Debrief by Julia

My Rewards