What do all four of these types of molecules have in common?

a. they contain instructions.

b. they are motors for movement.

c. each is only involved in an organism's physical structure.

d. they all contain carbon as an important part of their structure.

the answer is b because, investigating whether another species of moth also drinks tears might be interesting, but it would not directly explain why this species of moth does.

to explain why this species of moth drinks tears, the scientist could ask: "what nutrients that moths need are in elephant tears? "

the scientist could experiment with moth repellent or oter ways to keep the moths away, but that would not answer his original question.