Incomplete dash of fuels produces many poisonous dash​

Incomplete combustion of fuels produces a very poisonous gas called carbon monoxide:Excessive inhaling of carbon dioxide gas can kill a person.

I don't know if this is correct, your question did not have much context.

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.