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

Which of the following gases is primarily produced by the action of anaerobic bacteria on sewage?

$A$: The chief component of biogas is $CH_4$.
$R$: Biogas plants are prepared on foreign technology.

Consider the following statements about methanogenic bacteria:
$I.$ Methanogenic bacteria are commonly found in the anaerobic sludge formed during sewage treatment.
$II.$ These bacteria also occur in the rumen of cattle,where they act upon cellulosic material to break down cellulose.
$III.$ They play a very important role in the nutrition of cattle by digesting cellulosic material.
Which of the statements given above are correct?

Which type of bacteria is present in the rumen (a part of the stomach) of cattle?

The type of gases produced in a biogas plant depends on which of the following?