What does the part labeled '$X$' in the given figure represent?

In India,biogas technology was developed by which of the following organizations?

Assertion $A$: Herbivores release methane gas into the atmosphere.
Reason $R$: Herbivores consume a cellulose-rich diet.
Which option is correct for Assertion $A$ and Reason $R$?

During biogas formation,which one of the following processes is $NOT$ involved in the anaerobic digestion of slurry?

If bacteria grow on cellulosic material,they produce a large amount of which gas?

Statement $P$: Bacteria produce methane gas due to metabolic processes like anaerobic respiration.
Statement $Q$: Bacteria act on starchy materials.