During the process of photosynthesis, some of the light energy absorbe

Question

During the process of photosynthesis, some of the light energy absorbed by chlorophylls is stored in the form of adenosine triphosphate (ATP); the rest is used for the removal of the electrons in water,  to then be used in the reactions that turn carbon dioxide into organic compounds .

(A) to then be used in the reactions that turn carbon dioxide into organic compounds

(B) which are then used in the reactions that turn carbon dioxide into organic compounds

(C) which are then used in the reactions, turning carbon dioxide into organic compounds

(D) then used in the reactions that turn carbon dioxide into organic compounds

(E) which the reactions that turn carbon dioxide into organic compounds then use

Bunuel · Accepted Answer

OFFICIAL EXPLANATION

During the process of photosynthesis, some of the light energy absorbed by chlorophylls is stored in the form of adenosine triphosphate (ATP); the rest is used for the removal of the electrons in water,  to then be used in the reactions that turn carbon dioxide into organic compounds.

(A) to then be used in the reactions that turn carbon dioxide into organic compounds

Incorrect.

This answer choice is stylistically flawed. The phrase  to then be used  is ambiguous and confusing, because it is not clear what it refers to, what will then be used -  light energy  or  electrons ?

Note, that this question focuses to a great extent on issues of correct style and clarity of expression, in addition to logic and correct grammatical form.

Look for an answer choice that is grammatically correct, logical AND most clearly expresses the nature and sequence of events in the process described.

(B) which are then used in the reactions that turn carbon dioxide into organic compounds

This answer choice corrects the ambiguity in the original question by using a relative clause ( which are then used ) instead of the non-conjugated form  to be used , making it clear that  electrons  are used in the chemical process.

The corrected sentence also makes the sequence clear: first the electrons in water are removed and  then  used in the chemical reaction.

Note that in this construction, the complex noun phrase  electrons in water  is plural (similar to x of y subject), and is correctly modified by the relative clause  which are then used , which uses a plural verb ( are ).

(C) which are then used in the reactions, turning carbon dioxide into organic compounds

Incorrect.

While this answer choice corrects the original ambiguity by using a  relative clause (which is then used)  instead of the non-conjugated form  to be used , it introduces a change of meaning.

In the original phrase  reactions that turn carbon dioxide   , the relative pronoun  that  is used to define what kind of reactions these are. By changing  that turn  to  turning  and separating it with a comma the phrase  tuning carbon dioxide    seems to describe the entire situation of using electrons, thereby conveying a different meaning.

Note, that this question focuses to a great extent on issues of correct style and clarity of expression, in addition to logic and correct grammatical form.

Look for an answer choice that is grammatically correct, logical AND most clearly expresses the nature and sequence of events in the process described.

(D) then used in the reactions that turn carbon dioxide into organic compounds

Incorrect.

This answer choice repeats the original stylistic flaw. The phrase  then used  is ambiguous and confusing, because it is not clear what it refers to, what is later used -  light energy  or  electrons ?

(E) which the reactions that turn carbon dioxide into organic compounds then use

Incorrect.

While this answer choice corrects the original ambiguity, it changes the meaning of the original sentence.

The original sentence states that  electrons  are  used in  the chemical reactions (i.e. the electrons are a part of the reactions), while this sentence states that  the reactions are  the ones who  use  the electrons (i.e. the reactions are those who manipulate the electrons).

nikhilvarekar · Answer

As far as i know, "which" directly refers to the ojbect preceding it, in our case it's water. 
"which are" then will refer to "water", causing sv disagreement.

Please correct my thinking.

bnairsurya · Answer

Answer B would be correct if water is used in the carbon dioxide process

Crytiocanalyst · Answer

(A) to then be used in the reactions that turn carbon dioxide into organic compounds
to isn't the right usage it was not intended to do something but rather which was used to do something

(B) which are then used in the reactions that turn carbon dioxide into organic compounds
This is the intended meaning and the clauses are also perfect

(C) which are then used in the reactions, turning carbon dioxide into organic compounds
turninig isn't the right usage it distorts the meaning

(D) then used in the reactions that turn carbon dioxide into organic compounds
which is required after water so that the premise is connected to water

(E) which the reactions that turn carbon dioxide into organic compounds then use
after which what's being is used we cannot figure out

Therefore IMO B

sharmisthamona2 · Answer

I believe comma which can jump over prepositions like X of Y, which - here which refee X or Y whichever is logical
Education Aisle once shared a pdf on that.
 EducationAisle

Posted from my mobile device

alaawaku · Answer

How do we know that it is the electrons that are used in the reactions, but not "the rest of the energy" or "water"

DmitryFarberMPrep · Answer

alaawaku

Part of that is meaning. Even if we're not scientists, we might notice the logical sequence: First, electrons are removed. Then, those electrons are used for reactions. It's not clear why the electrons need to be removed from water, if the sentence then just says that water is used. We'd need to see something about this altered water in particular. As for "the rest of the energy," it already got used in the first part, so it wouldn't be used again.

There's also the proximity issue. "Which" can definitely modify "water," but it wouldn't go all the way back to modify the subject, "the rest."

However, the most important thing here is that those other interpretations only matter if they lead us to another answer that would then be valid. A and D aren't clear (what is used?), so changing the intended target of the modifier doesn't make any difference. B and C have "are," which only works if we're referring to "electrons." E could in theory be talking about water. However, as with A and D, changing the noun involved doesn't really make E any better. The main issue is the weirdness of saying "which the reactions use." Making the water get used in place of the electrons doesn't really change the overall validity of the answer.

During the process of photosynthesis, some of the light energy absorbe

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GMAT Sentence Correction (SC - EA only) Questions

During the process of photosynthesis, some of the light energy absorbe

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

More than Quant/Verbal Abilities: Speed vs. Accuracy

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