Which of these is a compound?
a. carbon dioxide
b. air
c. carbon
d. oxygen

Which of these is a compound?

Answer : A. Carbon dioxide

Explanation : Carbon dioxide is a compound of carbon and oxygen. A compound is a new substance formed by a reaction between components.

Air is mainly homogeneus mixture of nitrogen and oxygen, chemical elements. The components of a mixture can be separated once they have been combined.

Carbon is a chemical element.

Oxygen is a chemical element.

Hope this helps!

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.