Which of the following represents the gas holder in the given biogas plant diagram?

$A$: Biogas is a mixture of various gases.
$R$: The type of gases produced depends on the microbes and the organic substrate used.

Which one of the following reactions occurs during the process of solubilization in biogas production?

In India,the technology of biogas production was developed mainly by the efforts of which organizations?

Which is produced during anaerobic fermentation of agricultural wastes?

Methanogens,particularly $Methanobacterium$,grow anaerobically on cellulosic material and produce:
$I.$ Methane
$II.$ Carbon dioxide
$III.$ Oxygen
$IV.$ Ethane
Choose the correct option.