Why hydrated CuSO4 is blue while anhydrous CuSO4 is white??

The correct answer is - water acts as a ligand that splits d orbitals.

Explanation:

Hydrated CuSO4 has a central metal (Cu) surrounded by the water molecules, here water molecules play a role of the ligands that causes the splitting of d-orbitals. This splitting brings d-d transition and emits the blue color of Cu in the visible light.

Anhydrous CuSO4 on other hand is colorless due to the lack of molecules of ligand that makes splitting of d orbitals impossible so no transition of d-d orbitals takes place and no emission of color.

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.