Each battery has an emf of 1.6 volts. each wire is 24 cm long, and has a diameter of 0.0007 meters. the wires are made of a metal which has 7e+28 mobile electrons per cubic meter; the electron mobility is 4e-05 (m/s)/(v/m). a steady current runs through the circuit. the locations marked by "x" and labeled by a letter are in the interior of the wire.

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.