What is matter? What eventually happens to a gas if its pressure is increased?

Anything which occupies space and has mass and offer some resistance is called as Matter.

If a pressure on a gas goes on increasing then after certain point it begans to gets liquified,ie, converts into liquid.

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.