A characteristic of a nebula is O it is the center of the solar system.
o it is a region where stars are born.
o it forms halfway through a star's life cycle,
o it has the coolest temperatures in space.

not clear

the answer is na (sodium)

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.