These restrictions put a strain on the hospital's generators and

A. generators and the water supply and sewage system, which both depend,

Here the usage of both. creates confusion.

Can someone please explain why d is not correct and why a is correct?

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I chose E because the clause at the end of the sentence refers to 2 things/groups ('both')
In that option, the two groups are explicit ie generators & water supply and sewage system.
Please explain how this option is trumped by A

Hi Sayantan1604, while I agree that option A is perhaps not articulated in the best possible manner, E is definitely not correct because E is (what's called) a run-on sentence: Two Independent clauses connected by just a comma.

In E, following are the two Independent clauses connected by just a comma:

i) These restrictions put a strain on the hospital's generators as well as on the water supply and the sewage system

ii) Both depend on electric pumps

Kindly note that this is an important concept, and is quite frequently tested on GMAT. Hence, a robust understanding of run-on sentences is crucial.

p.s. Our book EducationAisle Sentence Correction Nirvana discusses run-on sentences, their application and examples in significant detail. If you or someone is interested, PM me your email-id; I can mail the corresponding section.

Does anyone know why C is wrong?

Though I am not fully convinced, I picked A based on elimination of other choices.

A. generators and the water supply and sewage system, which both depend

here "the generators" and "the water and sewage system" are parallel - so 'which' points to both.
but I still wonder how generators depend on electric pumps.

B. generators and on the water supply as well as the sewage system, which depend

here the splitting of water supply and sewage system makes the 'which part' to only point the sewage system.

C. generators; the water supply and the sewage system, both depend

Making "the water supply and the sewage system, both depend" as a separate clause distorts the meaning as if strain is only on the generators.

D. generators, the water supply and the sewage system, both depending

here the '-ing phrase' is placed as if "putting the strain depends on the electric pump"

E. generators as well as on the water supply and the sewage system, both depend

"both depend on electric pumps" is a run on.

A. generators and the water supply and sewage system, which both depend


B. generators and on the water supply as well as the sewage system, which depend



C. generators; the water supply and the sewage system, both depend


D. generators, the water supply and the sewage system, both depending


E. generators as well as on the water supply and the sewage system, both depend

IMO, the correct answer should be C.

The use of semicolon joins two closely related independent clauses but i'm not sure about the comma(,) used before 'both depend'.

You are correct in applying the rule, but here the intended meaning changes plus the two elements become unrelated. Hence Option C is incorrect. - Don't just go by the rules, Hard GMAT SC Qs test meaning changes.

C changes the meaning to restrictions put a strain on only generators, while the original meaning is that these restrictions impact generators, Water and Sewage systems as these systems depend on electricity.

Hope its clear.

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