What cause chemical reactions to happen slowly

In order for a reaction to occur, there must be a collision between the reactants at the reactive site of the molecule. ... In general, the reaction rate is slower when the reactants are large and complex molecules.

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.