Several Pentagon contractor firms are working on a new class

[rakeshd347]

Several Pentagon contractor firms are working on a new class of ventilator masks, not just for emergency and cleanup workers but to prepare for outbreaks of dangerous viruses and still another growing threat: the accidental releases of nanoparticles, which are the infinitesimal, engineered fibers that are starting to be used in electronics, food, medicine, and more.

outbreaks of dangerous viruses and still another growing threat: the accidental releases of nanoparticles, which are the infinitesimal, engineered fibers
outbreaks of dangerous viruses and still another growing threat: the accidental releases of nanoparticles and the infinitesimal, engineered fibers
outbreaks of dangerous viruses and still another growing threat of the accidental releases of nanoparticles, the infinitesimal and engineered fibers
outbreaks of dangerous viruses and for still another growing threat: the accidental releases of nanoparticles, the infinitesimal and engineered fibers
outbreaks of dangerous viruses and to protect against still another growing threat of the accidental releases of nanoparticles and the infinitesimal and engineered fibers

Source: Veritas prep

[theCodeToGMAT]

My pick is [spoiler]{D}[/spoiler] .. what is the OA?

[rakeshd347]

My pick is [spoiler]{D}[/spoiler] .. what is the OA?

OA is indeed D. Whats your reasoning behind it.

[theCodeToGMAT]

I read all the choices and realized that "for"/"to" is present only in {D} & {E} to keep the parallelism. Secondly, "the infinitesimal and engineered fibers" is an prefect appositive for nanoparticles.

{A} - INCORRECT; "for" is missing to maintain the parallelism; "which are the infinitesimal, engineered fibers" is wordier.. better construct is " the infinitesimal and engineered fibers "
{B} - INCORRECT; "for is missing; "the accidental releases of nanoparticles and the infinitesimal" means that two things were released.
{C} - INCORRECT; "for" is missing; meaning has changed from threat to "threat of"
{D} - CORRECT
{E} - INCORRECT; "nanoparticles and the infinitesimal and engineered fibers " is awkward