According to one acid-base theory, the h2o(l) molecules act as

both an acid and base

Explanation: By Bronsted-Lowery acid base theory: proton Donor is acid and proton Acceptor is base.

Here H2O by donating the proton acts as acid.

H2O > H^+ + OH^-

And by accepting the proton acts as base

H2O + H+ > H3O+

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.