Which one of the following gases is not the component of biogas?

The correct answer is Option (2) → Carbon monoxide

Biogas is a mixture of gases made by microbes working without oxygen, for example in the sludge digesters of sewage plants and in cattle dung. It is mostly methane, with some carbon dioxide and hydrogen sulphide. It can be burnt as a fuel.

(1) Carbon dioxide — A component of biogas.

(2) Carbon monoxide — Not a component of biogas. The microbes in the digester do not make it.

(3) Hydrogen sulphide — A component of biogas.

(4) Methane — A component of biogas. It is the main one and the part that burns.

Note: A similar question was also asked in CUET (UG) 2026 on 06-06-2026 (Slot 1) and on 30-05-2026 (Slot 2).

NCERT Extract:
Microbes in Sewage Treatment – …