The coloration of insects can serve as camouflage, as in the case of green insects that spend their lives in or near foliage, or to warn predators, as in the case of insects colored in yellow and black, which often signals that it is poisonous.
(A) or to warn predators, as in the case of insects colored in yellow and black, which often signals that it is poisonous.
(B) or for warning predators, as in the case of insects that have yellow and black coloring, which often signals that it is poisonous.
(C) or as a warning to predators, as in the case of insects bearing a combination of yellow and black, which often signals that they are poisonous.
(D) or as a predator's warning, as in the case of insects that are colored yellow and black, which often signals that they are poisonous.
(E) or to warn predators, as in the case of yellow-and-black insects, which often signals that they are poisonous.
The first verb phrase of the sentence "can serve as camouflage" must be parallel with what follows "or". In the original sentence, however, "can serve as camouflage" and "to warn predators" are not parallel.
(A) This choice is the same as the original sentence.
(B) This choice is incorrect because of it does not remedy the faulty parallelism.
(C) CORRECT. This choice corrects the faulty parallelism by including "as a warning..."
(D) This choice is parallel because it fits the construction "as X or as Y." However, it also contains the incorrect construction "predator's warning" instead of the better "warning to predators" (the warning is to the predators; it doesn't belong to the predators). It also incorrectly uses "which", which should refer only to the previous noun, not to an entire action or clause.
(E) This choice is incorrect because it does not remedy the faulty parallelism.
Hi , I am not convinced with the last part of explanation for D ( use of "which") . Could some one please explain how "which" is referring to an action & if it is , how come it it right in option C .