1. Select the correct statement from the following. (a) Biogas is produced by the activity of aerobic bacteria on animal waste. (b) Methanobacterium is an aerobic bacterium found in rumen of cattle. (c) Biogas, commonly called gobar gas, is pure methane. (d) Activated sludge-sediment in settlement tanks of sewage treatment plant is a rich source … Read more NEET Practice Questions Environmental Issues 2017