A certain metal M forms a soluble sulfate salt M2(SO4) Suppose the left half cell of a galvanic cell apparatus is filled with a 450. mM solution of M2(SO4)3 and the right half cell with a 4.50 M solution of the same substance. Electrodes made of M are dipped into both solutions and a voltmeter is connected between them. The temperature of the apparatus is held constant at 30.0°C. Required:
a. Which electrode will be positive?
b. What voltage will the voltmeter show?

a corroding iron, if that's one of your choices

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.