the pressure a gas exerts on another object is caused by

a the chemical composition of the gas

b collisions between gas particles and the object

c collisions between gas particles

d the physical size of the gas particles

the answers would be

the first one and the second one

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.