Sentence Correction

The gyrfalcon, an Arctic bird of prey, has survived a close brush with extinction; its numbers are now five times greater than when the use of DDT was sharply restricted in the early 1970's.
A. extinction; its numbers are now five times greater than
B. extinction; its numbers are now five times more than
C. extinction, their numbers now fivefold what they were
D. extinction, now with fivefold the numbers they had
E. extinction, now with numbers five times greater than
This is GMATPREP question. Pls help narrow down to the correct answer. Also what are the errors in the wrong choices?
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Conversation between Student (Bold ) and Ron
one concern about parallelism: should choice "its numbers are now five times greater than" be "its numbers are now five times greater than those"? thanks


Ron:linguistically correct answer:
no, because 'when the use of ddt was...' is, or at least can be interpreted as, an adverb phrase (not an adjective phrase).
if the descriptive phrase placed there were an adjective phrase (or were being interpreted as one, at least), you'd want 'those' to assure a parallel construction.

functional answer:
no, because none of the five choices contain this construction.


Is that because the sentence with adv. phrase could omit "those" to be parallel?

Could you give us a specific example to illustrate the parallel construction with "adj. phrase"? Thanks.

Ron:
ok, here's the basic story: as with other forms of parallelism, you have to ensure that the grammatical constructions are matched up as closely as possible.

if you had "those when the use of ddt was...", that would be centered around the pronoun those, which stands for a noun. therefore, to be parallel with it, you'd want another noun-centered construction: "its numbers now".

the problem in this sentence, though, is that now is being used strictly as a stand-alone adverb, since it's separated from "its numbers" by the VERB "are". (we know that this verb isn't part of the parallel construction, since there's no parallel verb in the second part.)
therefore, "now" itself - an adverb - is the whole first part of the parallel construction. for parallelism to be completed properly, the second part must be another adverb or adverbial construction, and that's why we just want "when the use of ddt was..." (without those).

this particular instance is somewhat complicated, but it's still a special case of the very very basic premise of parallelism: make the 2 parts the same.

soundok wrote:
I think this is a subject comparison. Two numbers of different times are compared. In my view, "its numbers" rather than "now" is the whole first part of the parallel construction. So, adding "those" to the second part sounds reasonable. Please clarify.Thank you.


Ron:nope. i covered this above, but i'll recap:

you think that "its numbers now" is the first part of the parallelism.
that's not possible, though, because there's a verb ("are") stuck between "its numbers" and "now". since that verb doesn't have a counterpart in the second half of the parallelism, it cannot be included in the first part.
and you are certainly not allowed to cherry-pick "its numbers ... now" from either side of "are".

this leaves "now" as the only legitimate 1st half, since "its numbers" by itself doesn't make sense, and you aren't allowed to include the "are".

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Care to Process and Explain .