What is the difference between an atom an ion how to determine the charge

Explanation:

When an atom's outermost orbital gains or loses electrons (also known as valence electrons), the atom forms an ion. An ion with more protons than electrons carries a net positive charge and is called a cation. An ion with more electrons than protons carries a net negative charge and is called an anion

they are all solids.

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.