6Na+Fe2O3 yields 3Na2O+2Fe 1. the mass of solid iron is produced
2.the mass of excess reactant that remains after the reaction is complete

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.

stratosphere, is the answer for (apex)