Hello, Hero1kF. Apparently, I took this question on the 16th of last month, and I took 1:25 to choose (C). (I do not remember the question, but that is most likely because I go through so many each day through my work and Expert reply requests.) It is funny, you are the third person in about as many days to draw my attention to a modifier issue in which a noun has been morphed into an adjective. This one does so in a more transparent manner, since the noun atmosphere and its adjective atmospheric are dissimilar enough to tell the difference. (Here is my earlier post on a similar type of question, one in which the noun and adjective forms are identical; if you look just beneath my post, you will see a response by GMATNinja as well.)

In this question, I have no qualms with either carbon monoxide in the atmosphere or atmospheric carbon monoxide. In the context of the sentence, either one could be understood to mean the former. It is really just a red herring split that Manhattan Prep probably tossed in when the real issue is the modifier for grew (in choice (A)) or increased. It is pretty easy to pare the answers down to (C) and (E) on that split alone. All that remains at that point is the decision about where to place during the twentieth century, and logically, (C) wins out.

Remember, regardless of how many sentences contain a specific element, particularly one that was used in the original sentence, the only part of an SC sentence that cannot be negotiated is anything that is not underlined. Since the entire sentence is underlined here, we have to be especially careful in interpreting intended meaning.

Thank you for calling my attention to the question.

- Andrew
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david nguyen :

I just solved the question and was wrong. I chose E. After pondering over and over, the distinction is clear to me now.
In the option E it tells the levels of CO in the atmosphere during the twentieth century increased" - What does it mean? It means the level of X during the 20th century increased. This level was in the 20th century. It doesn't mean that the increment happened during 20th century. It simply tells 20th Century level increased. So the increase can happen on any time. May happen on 21st century. as per the option, we only know the level that was set during 20th century increased. Nothing on the timeframe of the action.

Whereas in Option C, it tells clearly Levels of atmospheric carbon monoxide increased sufficiently during the twentieth century It means it was increased sufficiently during 20th century. The action that is the increase happened on 20th century.

I hope this helps !!

Regards,
Arup Sarkar

iamdivs :

This may help you :

https://gmatclub.com/forum/carbon-monoxide-levels-in-the-atmosphere-grew-by-enough-of-an-increase-65186-20.html#p2645766

Regards,
Arup

How can " Levels of atmospheric carbon monoxide" ... "begin trapping heat radiating from the Earth" ?? It seems that among a variety of other errors, these all have logical predication issues, except possibly D, although even that is a stretch.

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