The complete combustion of which of the following substances produces carbon dioxide and water?
no
k2co3
c8h18
cahco3

C₈H₁₈

Explanation:

Octane is an alkane which which is combustible in air.

The combustion of octane C₈H₁₈ in sufficient supply of oxygen produces carbon (IV) Oxide and water only.

Sufficient supply of oxygen ensures there is complete combustion of octane.

2C₈H₁₈ ₍l₎ + 25O₂₍g₎ → 16CO₂₍g₎ + 18H₂O₍l₎

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.