Question

Select the correct statement from following:

• A. Activated sludge in settlement tanks of sewage treatment plant is a rich source of aerobic bacteria
• B. Biogas is produced by the activity of aerobic bacteria on animal waste (dung)
• C. Methanobacterium is an aerobic bacterium found in rumen of cattle
• D. Biogas, commonly called gobar gas, is pure methane

Answer 1

The correct option is A Activated sludge in settlement tanks of sewage treatment plant is a rich source of aerobic bacteria

Only 1 is correct, activated sludge contains Flocs (fungi and bacteria).
Biogas is not pure methane gas it contains $C{o}_2$ and other gases and also produced in anaerobic conditions, also Methanobacterium is a methanogen and is anaerobic.
Methanobacterium is a strict anaerobic bacterium found in the rumen of cattle.
Biogas, commonly called gobar gas, is a mixture of methane and other gases.