Strontium and barium have similar chemical properties because atoms of these elements have the same number of 1.protons
2.neutrons
3.electron shells
4. Valence electrons

4. Valence electrons

Explanation:

Strontium and barium have similar chemical properties because atoms of these elements have the same number of valence electrons.

The valence electrons are the outer shell electrons within an atom. Both strontium and barium belongs to the group of alkali -earth metals on the periodic table.

This group consists of elements with two valence electrons.

The number of valence electrons determines chemical properties.

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.