Which gases are produced during the sewage treatment process in the formation of biogas?

Which is the correct group of gases produced during aerobic digestion (biogas production)?

Study the following flow chart of biogas production and select the correct option for $A, B$ and $C$.
Stage $III$: $C$
Stage $II$: Organic acids $\xrightarrow{B}$ $C$
Stage $I$: Soluble compounds or monomers $\xrightarrow{A}$ Organic acids
(Note: The flow chart shows: Proteins,Fats,Cellulose,Hemicellulose $\rightarrow$ Soluble compounds or monomers $\xrightarrow{A}$ Organic acids $\xrightarrow{B}$ $C$)

In gobar gas,the maximum amount is that of

Biogas is a mixture of inflammable gases like

The major component of biogas is .......