Analogous organs: coevolution or opportunism?
I think the question you have to answer is a bit badly phrased. Overall, I mainly agree with you, except for point A. Here are my comments for each points:
A
co-evolution is defined for the evolutionary dynamic between two lineages. It is typically not used to talk about two body parts. Consider for example the definition from Understanding evolution:

The term coevolution is used to describe cases where two (or more) species reciprocally affect each other's evolution.

, wikipedia

In biology, coevolution occurs when two or more species reciprocally (&quot;co-&quot;) affect each other's evolution.

or dictionnary.com

evolution involving a series of reciprocal changes in two or more noninterbreeding populations that have a close ecological relationship and act as agents of natural selection for each other, as the succession of adaptations of a predator for pursuing and of its prey for fleeing or evading.

I would note that the term coevolution can sometimes be used in its border line case as in this paper for example. It is particularly confusing as the term co-adaptation is sometimes used to talk about the interaction of two phenotypic traits. But stil, I would NOT check A
B
I agree with you! The conclusion is not valid from the premise (which means that it is not necessarily true, so even if the conclusion may be true, it cannot be concluded from the premise)
C
I agree with you! The statement is a bit unclear.
Typically, evolution is opportunistic would mean that throughout evolution history, a lineage may well evolve to reuse an existing gene for another purpose (neofunctionalization for example) which is very likely what happened here.
D
I agree with you! The conclusion is not valid from the premise.
In short
I would check C.