Carbon monoxide levels in the atmosphere grew by enough of

Question

Carbon monoxide levels in the atmosphere grew by enough of an increased percentage during the twentieth century that it began to trap heat radiating from the Earth, and it caused the average surface temperature to rise.

Carbon monoxide levels in the atmosphere grew by enough of an increased percentage during the twentieth century that it began to trap heat radiating from the Earth, and it caused the average surface temperature to rise.
Carbon monoxide levels in the atmosphere increased by enough of a percentage during the twentieth century that they began to trap heat radiating from the Earth, causing the average surface temperature to rise.
Levels of atmospheric carbon monoxide increased sufficiently during the twentieth century to begin trapping heat radiating from the Earth, causing the average surface temperature to rise.
Atmospheric carbon monoxide levels increased by a sufficient percentage during the twentieth century to begin trapping heat radiating from the Earth, which caused the average surface temperature to rise.
Levels of carbon monoxide in the atmosphere during the twentieth century increased enough to begin trapping heat radiating from the Earth, causing the average surface temperature to rise.

maratikus · Answer

I think it's C because "levels increased during 20th century" sounds better than "levels during 20th century increased"

abhijit_sen · Answer

OA is C.

GMAT TIGER · Answer

Defginitely C.

note two differences:

1. sufficient (C) is preferred over enough (E).
2. placement of time (during the twentieth century) after adverb (C) is better than before it (E).

gurpreetsingh · Answer

I m unable to understand the subtle difference between C and E because of the placement of the phrase'During the 20th century'

guys pls explain it to me...

imania · Answer

I went for C, dunno why indeed C dominates E!
increased enough to ... sounds weird to me...

methevoid · Answer

My 2cents - 
In the original sentence -'during the twentieth century' is talking about the increase in quantity of CO,

In E, use of phrase - 'during the twentieth century' after - 'Levels of CO in the atmosphere' 
 is implying that the Level of CO during the 20th century, which i suppose is distorting the original meaning,

thus C by placing 'during the twentieth century' after 'increased sufficiently'
 correctly follows the intended meaning.

gurpreetsingh · Answer

X increased sufficiently during the twentieth century

X during the twentieth century increased enough

Do not consider sufficiently and enough for the comparison. Don't you think both implies same thing? or I m missing something?

methevoid · Answer

I guess, no it doesn't imply the same thing, 
E.g.

phrase 2 cannot modify   directly until its separated by commas or phrase 1 and phrase 2 are connected by conjunctions.

gurpreetsingh · Answer

could you explain me what both the sentences are implying by comparing them?

methevoid · Answer

Okay,

Let us look it this way, "during the 20th century" is an adverbial modifier, which should predominantly modify an adverb, in C it does so by modifying 'increased sufficiently' 
but 
in E -"during the 20th century" modifies -Levels of CO.

gurpreetsingh · Answer

It makes sense!! But in a short span of time I might be looking for the right meaning. But I m unable to interpret how these are different in meanings if I do not look at the logic of adverb, which can not modify noun.

Could explain me by giving example what does the two sentences means in layman language.

Thanks for your efforts !! +1

methevoid · Answer

well...i re read and again re read d sentence, there seems no difference as such in meaning....

only thing i cud think was Adverbial modifier!!! thnx gurpreet dat was nice to discuss.

Carbon monoxide levels in the atmosphere grew by enough of

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