This is essentially a test of 1. the use of such as versus like 2. the parallelism of the coordinate conjunction either--- or and 3 the parallelism of a participle or gerund and noun

A like malaria and dengue have focused either on the vaccination of humans or on exterminating--- like can not be used to mark examples

B like malaria and dengue have focused either on vaccinating of humans or on the extermination of----use of like is wrong

C. as malaria and dengue have focused on either vaccinating humans or on exterminating--- either vaccinating humans or on exterminating---wrong parallelism of either ---or coordinate conjunction; on the right hand side of both either and or, similar structure should be used

D as malaria and dengue have focused on either vaccinating of humans or on extermination of----- either vaccinating of humans or on extermination of --- bad co-ordinate conjunction parallelism.

E as malaria and dengue have focused on either vaccinating humans or exterminating --- proper use of either or parallelism. Correct choice.

Now let us take choice B. We rejected it primarily because of the uses of like. However, how about either or parallelism? It is perfectly parallel because of the use of the pronoun on the right hand side of both either and or.

What about vaccinating of and extermination of—this is also perfectly parallel because vaccinating of is a gerund and is as good as extermination of in structure.
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Dear Friends,

Here is a detailed explanation to this question-

Concepts tested here: Parallelism + Idioms

• “neither A nor B” and “either A or B” are idiomatic uses and are only used when referring to two elements; A and B must be parallel.
• “like” is used for comparing nouns, “as” is used for comparing actions/clauses, and “such as” is used for giving examples.

A: This answer choice fails to maintain parallelism between A ("on the vaccination of humans") and B ("exterminating mosquitoes with pesticides") in the idiomatic construction "either A or B"; please remember, “neither A nor B” and “either A or B” are idiomatic uses and are only used when referring to two elements; A and B must be parallel. Further, Option A incorrectly uses the unidiomatic construction "such...like" to provide the examples of "malaria" and "dengue"; please remember, “like” is used for comparing nouns, “as” is used for comparing actions/clauses, and “such as” is used for giving examples.

B: This answer choice incorrectly uses the unidiomatic construction "such...like" to provide the examples of "malaria" and "dengue"; please remember, “like” is used for comparing nouns, “as” is used for comparing actions/clauses, and “such as” is used for giving examples.

C: This answer choice fails to maintain parallelism between A ("vaccinating humans") and B ("on exterminating mosquitoes with pesticides") in the idiomatic construction "either A or B"; please remember, “neither A nor B” and “either A or B” are idiomatic uses and are only used when referring to two elements; A and B must be parallel.

D: This answer choice fails to maintain parallelism between A ("vaccinating of humans") and B ("on extermination mosquitoes with pesticides") in the idiomatic construction "either A or B"; please remember, “neither A nor B” and “either A or B” are idiomatic uses and are only used when referring to two elements; A and B must be parallel.

E: Correct. This answer choice correctly maintains parallelism between A ("vaccinating humans") and B ("exterminating mosquitoes with pesticides") in the idiomatic construction "either A or B". Further, Option E correctly uses the idiomatic construction "such...as" to provide the examples of "malaria" and "dengue".

Hence, E is the best answer choice.

To understand the concept of "Like" vs "As" on GMAT, you may want to watch the following video (~1 minute):



To understand the concept of "Either-Or" and "Neither-Nor" on GMAT, you may want to watch the following video (~1 minute):



All the best!
Experts' Global Team
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Correct: Proper idiomatic phrase is used "such . . .as", and "vaccinating" and "exterminating" are parallel

I narrowed it down between D and E due to the idiomatic use of such x as Y and proper parallel structures

then I chose E because I know the GMAT prefers active over passive voice.

As an addendum to my earlier posting, let may say that all the five choices in the context are active voice sentences; so the use of active versus passive voice is not tested here. In addition, Choice C, D and E use the template: such as x and y and not such x as y
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so then what is the grammatical distinction, if any, between the structures:

vaccinating of humans
vaccinating humans?

I'm guessing vaccinating humans would be preferred if all else equal?

also is it just me, or does the SC section seem to have a LOT of parallel error type questions?? Even questions with other errors seem to contain parallel errors along with some other error eg. parallel errors + verb tense

Merely saying vaccinating may mislead. Used as an adjectival phrase, vaccinating humans may refer to those humans who do the job of vaccination. Vaccinating is a present participle and not a gerund in that instance. However, vaccinating of humans is out and out a gerund. That is why for use as a gerund, we may add the preposition of to be sure

Parallelism error is one of the most used aspects of sentence structure at least in GMAT. Although purely singular errors such as lack of parallelism alone may appear rarely in GMAT, the normal practice often is to cobble two or three errors together, of which parallelism will be one either as the primary error or as a secondary error.
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So to take this further, simple and complex gerunds cannot be parallel and if we change vaccinating humans to:
I am vaccinating humans now then it turns into a simple gerund if vaccinating humans modifies a noun. Gotchya.

I am vaccinating is not used in the sense of gerund which i a noun. Because of the addition of am to the present participle vaccinating, I am vaccinating turns into a present progressive, which is a verb.

If you have any further doubts, you may perhaps like to read some good guide on the verbals namely present and past participles, gerunds and infinitives – may be MGMAT’S SC guide.
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Concept tested: Idioms, Special construction
Difficulty: 650
Illustration: Proper idiomatic construction rules say that
1. Such as is preferred to like
2. Either X or Y is the correct idiomatic structure provided X and Y are parallel.
Using 1, we can A and B are eliminated
Using 2, we can eliminate C and D
E is the correct answer

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In GMAT English "such as" is to be used always to present a list, not "like".
Hence (A) and (B) incorrect.

Secondly -Correct usage of Either "X" or "Y" - X and Y should be in same form

C and D put incorrect "on" before exterminating.

Hence

+1E

On either…or is correct
Either on…or on…..is also correct (I suppose)
On either…or on is not correct, eliminate C and D

Like presents comparison
As presents examples, eliminate A and B


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Hey folks!
I have a simple question on which I, as a non-native speaker, am having some difficulties.
We all know that according to parallelism, all parallel clauses should begin with the same preposition or relative clause, but I have seen so many confusing structures, I had to ask this question:

Consider the following sentence:
I lost my final paper, to which I have spent great effort and a great sum of money. (Disregard the meaning since I couldn't come up with a scenario )

As the meaning is clear here we opted to not repeat "to which". But when should one repeat the clause or the preposition?
I was also going the ask the 138th SC from OG13, but I figured it out, so I'll be glad if you could reaffirm me:

Most efforts to combat such mosquito-borne diseases like malaria and dengue have focused either on the vaccination of humans or on exterminating mosquitoes with pesticides.

A and dengue have focused either on the vaccination of humans or on exterminating
B like malaria and dengue have focused either on vaccinating of humans or on the extermination of
C as malaria and dengue have focused on either vaccinating humans or on exterminating
D as malaria and dengue have focused on either vaccinating of humans or on extermination of
E as malaria and dengue have focused on either vaccinating humans or exterminating

Since the paralellism should be between two clauses of either.... and or.... the OA is E. But what if C was something like "as malaria and dengue have focused on either vaccinating humans or exterminating" (without the 2nd "on")
Would that be also true?

I know I could have been clearer with the question I asked, but I think the experts here will understand what I mean.
I gladly await your response in my final day before the GMAT :D

Thanks in advance,
Cinar

There is one simple rule of correlative conjunction parallelism that you should be conscious about. The correlative conjunction parallelism involves the following pairs.

1. Either or
2. Neither nor
3. Not but
4. Not only but also
5. Not by but by
6. Both and
7. Not because but because

The thumb rule to note while using correlative, is that whatever form or structure is used after ( or the right side of ) the first arm of the pair should also be used after the right side of the second arm.

a. Eg: He is going either to England or to Ireland’ This is the correct form as the word to is used after both either and or ‘ It is wrong to say - he us going to either England or to England

He is not only singing well but also dancing well; ing form used on the right side of both not only… but also. It is wrong to say – he singing not only well but also dancing well.

To come to your example from OG (limiting just to correlative conjunction //ism): This is using either or; The same form that comes after either should be used after or;

A like Malaria and dengue e have focused either on the vaccination of humans or on exterminating ------- on the vaccination and on exterminating – not//--; on the vaccination of humans or on exterminating of mosquitoes is parallel.

B like malaria and dengue have focused either on vaccinating of humans or on the extermination of--- on vaccinating or on the extermination of is unparallel; on the vaccination of humans or on exterminating of mosquitoes will be parallel.
(more importantly, A and B use like for comparison, which is not acceptable)

C as malaria and dengue have focused on either vaccinating humans or on exterminating ---- either vaccinating humans or on exterminating—UN//.

D as malaria and dengue have focused on either vaccinating of humans or on extermination of --- either vaccinating of humans or on extermination of---UN//

E as malaria and dengue have focused on either vaccinating humans or exterminating --- correct //ism.

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Hi

I just did this question but did not focus on the "such...as" idiom. Instead, I tried to figure out whether we should use "like" vs "as".
In my notebook I wrote down, that "like" can only compare nouns, pronouns and noun phrases, whereas "as" can only compare clauses.

Here, the comparison is b/w "malaria" and "dengue" (both are nouns), so I went with A or B.

Can someone please clarify/help with understanding?

Thanks and best regards

Well, your clarified yourself actually because indeed the structure is such...as.

Also, the usage of like would be inappropriate because there is no comparison here. Malaria and dengue are just given as two examples of mosquito-borne diseases. This is a very classical usage of such as: to give examples.

p.s. Our book EducationAisle Sentence Correction Nirvana discusses as/like/such as, their application and examples in significant detail. If someone is interested, PM me your email-id, I can mail you the corresponding section.
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Is such x as y even a separate idiom? I thought it meant the same as such as x and y.

Such X as Y is different from such as X and Y. The former refers to the intensity while the latter is used to state examples.
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Most efforts to combat such mosquito-borne diseases like malaria and dengue have focused either on the
vaccination of humans or on exterminating mosquitoes with pesticides.

A. like malaria and dengue have focused either on the vaccination of humans or on exterminating
Usage of “like” to present examples is incorrect

B. like malaria and dengue have focused either on vaccinating of humans or on the extermination of
Same error as in option A

C. as malaria and dengue have focused on either vaccinating humans or on exterminating
Parallelism Error : “on either VH or ET” is correct …since “on” is outside the “either..or” structure

D. as malaria and dengue have focused on either vaccinating of humans or on extermination of
Parallelism Error : “on either VH or ET” is correct …since “on” is outside the “either..or” structure

E. as malaria and dengue have focused on either vaccinating humans or exterminating
Correct
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