Which of the following observations indicates that atoms of all elements contain small, negatively charged particles? a - alpha particles are repelled by cathode rays of elements. b- cathode rays are deflected towards a positively charged rod. c- a particular frequency of light is produced by a gas in an excited state. d- certain areas of the atom called orbitals contain all the charged particles.

oh i thought it was talking about electrons so i would have put :  A, particular frequency of light is produced by a gas in an excited state.

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.