atomic mass of an element is mass of an atom of the element but this quantity is an average mass only. why?​

atoms are the smallest building blocks of elements, the reason why its an average mass is because its so so light to have an 'accurate' and straight forward mass.

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.