Copper metal is added to a solution of silver nitrate. copper nitrate forms and the colorless solution turns blue. two of the physical properties of copper nitrate are a. blue color and low density. b. soluble in water and low boiling point. c. low density and low boiling point. d. blue color and soluble in water.

The question gives no information regarding the density or boiling point of copper nitrate, so you can rule out anything that mentions those properties. This leaves D. blue color and soluble in water, which fits because the copper nitrate was in solution and was blue.

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.