I have seen some questions where even though

I have seen some questions where even though "which" has a prepositional phrase just before it and its usage is correct ...



I took Mnahattan gmat test(see example below from it) and the OA is C. Even though D uses "which" its usage is not correct according to the explanation but its correct in choice C.







The explanation of choice C says that which can refer to noun before the preopositional phrase too in some cases so in choice C it refers to "combination" and not "black"...It is the combination of yellow and black (of yellow and black - prepositional phrase) which signals that the insects are poisonous...



Where as the elimination of choice D says the usage of "which" is incorrect since noun before the clause " that are colored yellow and black " is " insects" and therefore insects cannot signal they are posionous...



This explanation had confused me too much and i do not know whats the proper use of which ...





Do we need to scan nouns if there is a prepositional phrase just before "which" like =>

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.





In the above example "combination" is the noun so which refers to combination so its usage is correct...



whereas in choice d its choice is incorrect....



Please shed some details on how this works and please please explain in full details... Thanks in advance for your help!!!







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.