The airline company, following through on recent warnings

IMO C
Parallelism. explanation as above.

Kindly explain the logic behind choosing option C as I could not find any earlier explanation on option C.

The airline company, following through on recent warnings that it might start reducing service, announced that it was eliminating jet service to nine cities, closing some unneeded operations, and it grounded twenty-two planes.

(A) closing some unneeded operations, and it grounded
(B) closing some unneeded operations, and grounding
(C) was closing some unneeded operations, while it grounded
(D) it closed some unneeded operations and grounded
(E) it was closing some unneeded operations, and grounding

It should be "(B) closing some unneeded operations, and grounding"

A conjunction such as and must connect PARALLEL FORMS.
The airline company announced that it was:
ELIMINATING jet service to nine cities
CLOSING some unneeded operations
and
GROUNDING twenty-two planes.
Only B offers the required parallelism.

The correct answer is B.

Please note the following distinction:
The three VERBings that constitute a series of actions -- was eliminating, [was] closing, and [was] grounding -- all serve as VERBS.
The linking verbs in brackets are omitted, but their presence is understood.
But a VERBing without a linking verb such as was typically serves NOT as a verb but as a MODIFIER or as a NOUN.
Here, following -- a VERBing without a linking verb -- serves as an ADJECTIVE modifying the airline company.
WHAT KIND of airline company announced that it was eliminating jet service?
The airline company FOLLOWING THROUGH ON RECENT WARNINGS.

The best way to approach this ques is
1)ANNOUNCED = means its not completed yet . either its under process or it will be done . So grounded (past verb) isn't right fit
2)We always need to make llism list when the things are in list or belong to same subject . . So eliminating suggests we need ING verb
3)WAS will be common for 3 items in list .

Hence B is right choice .

There are a series of actions the company is doing and here the keyword is was eliminating
So using parallelism the other two options also should be in the same way eleminating, closing and grounding
So option B is correct

Posted from my mobile device

Hello from the GMAT Club VerbalBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.