Sentence Correction

Most Americans surveyed think that international environmental treaties are useless
now but that they will, or could, be useful in the future.

(A) that they will, or could,
(B) that they would, or could
(C) they will be or could,
(D) think that they will be or could
(E) think the treaties will be or could

OA : E .

But , I am not convinced with the OA . Please provide your explanations .

Thanks

I like E because it leaves you in no doubt about what could be useful. Because there are two plural nouns in the sentence, namely "Americans" and "treaties", grammatically there are two things that could be useful. Even though it seems obvious from the context that the treaties could be useful, not the Americans, it is still best to choose the option that make this 100% clear. The pronoun "they" in the other options does not achieve this clarity.