Which gas is responsible for greenhouse effect?

Some greenhouse gases are produced naturally and reach the atmosphere as a result of both natural processes.

Water vapor, carbon dioxide $\left({\mathrm{CO}}_2\right)$, methane $\left({\mathrm{CH}}_4\right)$, nitrous oxide $\left({\mathrm{N}}_2\mathrm{O}\right)$, and ozone are among the greenhouse gases that are produced by both human activity and natural occurrene.

Correct option is A.