During sewage treatment, gases produced include Methane, oxygene and hydrogensulphide. Methane, hydrogen sulphide, carbon dioxide and hydrogen. Hydrogensulphide, methane and sulphur dioxide. Hydrogen sulphide, nitrogen and methane.

Biogas contains a mixture of different gases which are produced by the breakdown of organic matter in the absence of oxygen. Biogas is composed of methane (CH4) and carbon dioxide (CO2) and may have small amounts of hydrogen sulphide (H2S), hydrogen (H2), moisture and siloxanes.Thus, the correct answer is option B.