Unlike the short flights of the shuttle and earlier spacecraft, which carried sufficient power in fuel cells and batteries, a permanently orbiting space station will have to generate its own electricity.

A. the short flights of the shuttle and earlier spacecraft, which carried sufficient power in fuel cells and batteries
B. the shuttle and earlier spacecraft, with sufficient enough power in fuel cells and batteries for their short flights
C. the short flights of the shuttle and earlier spacecraft, which enabled them to carry sufficient enough power in fuel cells and batteries
D. the shuttle and earlier spacecraft, which were capable of carrying sufficient power in fuel cells and batteries for their short flights
E. the flights of the shuttle and earlier spacecraft, whose shortness allowed them to carry sufficient power in fuel cells and batteries

Unlike X, Y is the correct construction, where X and Y are logical and parallel.

A. space station is compared with flights of shuttles. Apples to oranges
B. sufficient enough is a heavily redundant construction.
C. Same error as A
D. Correct.E. Same error as A and C.
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Correctly pointed out!

The reason B is wrong is that the prepositional phrase " with......." is unclear in terms of the clause/phrase it is modifying. Is it the previous one or the next one.

eg. XXXXXXXXX, with.........., YYYYYYYYYY

We dont know with is referring to XXXXXXXXX or to YYYYYYYY.


Hope this clarifies

i go with D

in GMAT,correct usage of unlike would be,

Unlike X<noun>,....,<Y><noun>....

Unlike X , Y is the idiom being tested here. Only B and D are the contenders. In B their is a modifier error , with is xxx is incorrect , further their is no verb present. D wins.

Apart from 'sufficient enough' which is redundant, is there any other issue in B?
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yea.

use of 'with' is unwarranted. You should use 'which' when you are presenting a non-essential information.

'with' is generally used when you want to use the modifier as well or show the modifier plays an important role.

see this question: the-javelin-has-a-sharp-point-which-is-more-obviously-137306.html

look at option B and E.
E means, because the javelin has a sharp point it is dangerous.
B means javelin has a sharp point AND it is dangerous. (states 2 facts about javelin without connecting them)

Isn’t this odd? Apart from that A, C and E are out because of a devilish comparison, and B is out due to a blatant redundancy error, we have still not reached the right choice. The only remaining choice D has errors that I would reckon are more serious than the redundancy of B. How?

D says ‘which were capable of’, using the past tense. This is a factual error. The shuttle and earlier spacecraft were not only capable in the past, but also today and may be ever. We must use a present tense to focus on this generalization of this aspect, rather than a past tense. Please note that the main clause itself is in the future perfect tense; so, use of past tense is not justified.

Secondly, it would be better to say actively that the shuttles and spacecrafts could carry sufficient power rather passively as ‘capable of carrying’.
Which error should we pardon: redundancy or wrong tense?
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Experts,

Can anyone clarify the quoted doubt?

Sure...first of all be careful with how you evaluate tense. There are many times when you have to maintain a certain tense by force (due to parallelism and perfect tenses), but tense shifts in themselves are not incorrect. They are only incorrect if they lead to improper/illogical meaning. There is nothing illogical in this sentence that creates a comparison between the historical capabilities of shuttles/space craft and the future needs of the space station.

As for the active vs. passive construction, the GMAT shows no preference for active construction. Passive construction is grammatically correct and should not be used for eliminations.

KW
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Some people argue that in option B the use of modifier "with..." is incorrect. Experts, please help me to explain why the use of modifier "with...." in option B is incorrect!! Thank you so much!
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NO !! this is not the case
this construction is not outright wrong but yes there is this construction "sufficient enough power" which makes it wrong .this expression is redundant ----->"sufficient" and "enough" implies the same meaning

does it help?

Unlike the short flights of the shuttle and earlier spacecraft, which carried sufficient power in fuel cells and batteries, a permanently orbiting space station will have to generate its own electricity.

The problem here is comparison. short flight is compared with a permanently orbiting space station. A,C and E choices are out due to this reason
Now we are left with choices B and D.

choice B - Use of With is unwarranted. Which clause should be used here and Sufficient & enough are redundant

Choice D is correct answer

A. the short flights of the shuttle and earlier spacecraft, which carried sufficient power in fuel cells and batteries
B. the shuttle and earlier spacecraft, with sufficient enough power in fuel cells and batteries for their short flights
C. the short flights of the shuttle and earlier spacecraft, which enabled them to carry sufficient enough power in fuel cells and batteries
D. the shuttle and earlier spacecraft, which were capable of carrying sufficient power in fuel cells and batteries for their short flights
E. the flights of the shuttle and earlier spacecraft, whose shortness allowed them to carry sufficient power in fuel cells and batteries

[ Excuse my obvious question. I want to make sure I understand which statements.

In the correct answer choice sentence, "Unlike the flights of the shuttle and earlier aircraft, which were capable of carrying..."

"Which" refers to "flights of the shuttle and earlier aircraft," or "shuttle and earlier aircraft," or "earlier aircraft?"

Basically, if a question asks, "Unlike x and y, which blah blah blah," can I understand that which refers to "x and y" rather than just "y? ]

Hi Experts I am re-posting the doubt asked by Banaorange. What is 'Which' referring to here? As it is a pronoun, it should refer to only one antecedent and that also with no ambiguity. Here it is not clear. How can 'Which' refer to both shuttle and earlier aircraft??

Please help. As a non native, I am very confused about such rules. Whether they are hard rules or are flexible?

With "shuttle and earlier aircraft" you are dealing with a compound noun. This compound noun is viewed as a single, plural grouping. It would take a plural verb and can be referred to as a grouping with "which".

KW
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Hi Kyle,

Thanks for the reply.

I checked more on compound noun and how it is made by combining at least one noun and another noun or adjectives.

So does it holds true for any pronoun such as that, whom, when, who etc. They can refer to a compound noun in a sentence just like which does?

Correct idiomatic usage of Unlike is -

Unlike X , Y ( Where X and Y are both Nouns.)

A. the short flights of the shuttle and earlier spacecraft, which carried sufficient power in fuel cells and batteries - Incorrect
B. the shuttle and earlier spacecraft, with sufficient enough power in fuel cells and batteries for their short flights - Incorrect
C. the short flights of the shuttle and earlier spacecraft, which enabled them to carry sufficient enough power in fuel cells and batteries - Incorrect
D. the shuttle and earlier spacecraft, which were capable of carrying sufficient power in fuel cells and batteries for their short flights - Correct

Unlike the shuttle and earlier spacecraft,which were capable of carrying sufficient power in fuel cells and batteries for their short flights, a permanently orbiting space station will have to generate its own electricity.

E. the flights of the shuttle and earlier spacecraft, whose shortness allowed them to carry sufficient power in fuel cells and batteries - Incorrect

Hence IMHO (D)
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These relative pronouns can refer back to either a singular or plural antecedent and the antecedent could be a compound noun (plural). You need to be aware of number agreement with the personal/impersonal pronouns that show do indicate number: he, she, it, its, they, them, their.

KW
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Unlike the short flights of the shuttle and earlier spacecraft, which carried sufficient power in fuel cells and batteries, a permanently orbiting space station will have to generate its own electricity.

"short flights of the shuttle and earlier spacecraft" which makes it plural, so i think using "whose" make it sound better than using which. Please clarify

"Which" is both the plural form and the singular form.
The pen, which you gave me, is lost.
The pens, which you gave me, are lost.

"Whose" is also both the plural form and the singular form, but in possessive. Note that "whose" is the possessive form of both "which" and "who".

The briefcase, whose handle is broken, is lost. (possessive of "which" - singular)
The briefcases, whose handles are broken, are lost. (possessive of "which" - plural)
The girl, whose father came yesterday, is sick. (possessive of "who" - singular)
The girls, whose fathers came yesterday, are sick. (possessive of "who" - plural)