I would go with (C) for the following reasons:

(i) "with its mouth parts implies you're talking about "the dermestid beetle" vs "dermestid beetles" (so you can knock out choices A & B)
(ii) E gets knocked out because it seems wordy to say "and it pulls"
(iii) parallelism with the verb "feeds" and "pulls" (vs. pulling) can be found in choice C

What's the correct answer?

As ReenaMo Mentioned the first split we can make is between
"dermestid beetles" and "the dermestid beetle".

The non underlined part of the sentence uses the pronoun `its`,
this gives us the clue that the referent is a singular , that is " the dermestid beetle"

We can safely eliminate option A and B.

Second thing to look out for is the coma and the modifier following it.
In this case the modifier pulling is correct as it descibes HOW the action performed on the decaying flesh.

Therefore the correct answer should be D.

If we consider option C , it means that the beetle feeds and also pulls. two different things. But the sentence implies that pulling is a result happening due to feeding.

Option D provides clarity in meaning.

Ans : D

IMO:D

imo:D

IMO: D