What must happen for an electron to move to a higher energy level?
o
the electron must gain energy
o
the electron must transfer energy to another electron.
the electron must release energy through fission.
o
the electron must collide with the nucleus.

The electron must gain energy.

Explanation:

For a electron to be promoted from one energy level to a higher energy level it has to absorb energy. If the electron decay back to the initial energy level will emit a photon with the a energy equal of the difference between the two energetic levels.

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.