Owls have elongated eye tubes that are efficient at collecting and processing light, which makes it easier for them to see clearly at night.

(A) which makes it easier for them -> "which" modifies "processing light", it doesn't make sense. Incorrect.

(B) which makes it easier for it -> "which" modifies "processing light", it doesn't make sense. and another issue of use second "it" (singular pronoun) for Owls (plural noun). Incorrect.

(C) making it -> Incorrect.

(D) making it easier for the owls -> I find, this is better as, we have "making" modifies the process. Let's keep it.

(E) making it easier for it -> "it" (singular pronoun) for Owls (plural noun). Incorrect.

So, I think D.

Hey guys,

I think the answer is D here. "Which" in A + B would wrongly refer to the light. D is the only answer referring to the owls (plural).

One question from my side: Does the prepositional modifier in D refer to the relative pronoun clause starting with "that"?

IMO it does as the doer of this clause are the "elongated eye tubes". Please, correct me if I'm wrong.

Cheers
Rudolf

Owls have elongated eye tubes that are efficient at collecting and processing light, which makes it easier for them to see clearly at night.


(A) which makes it easier for them Incorrect

which modifies collecting and processing light that is not intended meaning, whole clause is the fact

(B) which makes it easier for it Incorrect

same as A
it singular, owls plural

(C) making it Incorrect

missing easier

(D) making it easier for the owls Correct

(E) making it easier for it Incorrect

it singular, owls plural