verb structure help- present perfect and 2nd ing verb

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msbelasco: Senior | Next Rank: 100 Posts; Posts: 32; Joined: Fri Jul 27, 2012 10:18 am; Thanked: 1 times

by msbelasco » Fri Aug 17, 2012 6:11 am

OG SC #134

Recently implemented "shift-work equations" based on studies of the human sleep cycle have reduced sickness, sleeping on the job, fatigue among shift workers, and have raised production efficiency in various industries.

the correct answer is

and fatigue among shift workers was lowered while raising

My question is what is the rule with parallelism here. Why is it not incorrect to use the ing verb "raising" with the present perfect "have reduced" in the first part of the sentence? I thought these two verb structures have to match. Any help would be greatly appreciated. Thanks!

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Source: Beat The GMAT — Sentence Correction | Fri Aug 17, 2012 6:11 am

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by GMATGuruNY » Fri Aug 17, 2012 7:00 am

Recently implemented "shift-work equations" based
on studies of the human sleep cycle have reduced
sickness, sleeping on the job, fatigue among shift
workers, and have raised production efficiency in
various industries.

(A) fatigue among shift workers, and have raised
(B) fatigue among shift workers, and raised
(C) and fatigue among shift workers while raising
(D) lowered fatigue among shift workers, and raised
(E) and fatigue among shift workers was lowered
while raising

Please post the entire SC, along with the answer choices.

Note the SPLIT in the answer choices:
C and E begin with and; A, B and D do not.
Determine the correct position for and.
Here, "shift-work equations" have reduced THREE THINGS: sickness, sleeping on the job, fatigue among shift workers.
AND must be placed before FATIGUE, the last item in the list.
Eliminate A, B and D.

In E, have reduced and was lowered are redundant.
Eliminate E.

The correct answer is C.

In the OA, while raising serves as a MODIFIER.
A modifier does not need to be parallel with the main verb of the sentence.

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