Stone flies are not bioindicators. Bioindicators provide a range of techniques to assess the impacts of air pollution from reactive nitrogen (N) compounds on statutory nature conservation sites. They complement physical monitoring of atmospheric concentrations and deposition and risk assessment based on the critical loads approach by providing site-based information on atmospheric N concentrations, N deposition and/or ecological impacts.

Correct Option: B

Stone flies are not bioindicators. Bioindicators provide a range of techniques to assess the impacts of air pollution from reactive nitrogen (N) compounds on statutory nature conservation sites. They complement physical monitoring of atmospheric concentrations and deposition and risk assessment based on the critical loads approach by providing site-based information on atmospheric N concentrations, N deposition and/or ecological impacts.

More value of BOD means the water sample is polluted by organic matter. BOD of distillary effluent is 40000 mg/L and that of paper mill effluent and sewage is 190 mg/L and 30 mg/L respectively.

Correct Option: B

More value of BOD means the water sample is polluted by organic matter. BOD of distillary effluent is 40000 mg/L and that of paper mill effluent and sewage is 190 mg/L and 30 mg/L respectively.

In secondary treatment mainly settled sewage flows to an aerobic biological treatment stage where it comes into contact with micro-organisms which remove and oxidise most of the remaining organic pollutants.

Correct Option: D

In secondary treatment mainly settled sewage flows to an aerobic biological treatment stage where it comes into contact with micro-organisms which remove and oxidise most of the remaining organic pollutants.

Marsh gas is another term for methane, produced by plants decomposing under water.

Correct Option: D

Marsh gas is another term for methane, produced by plants decomposing under water.

Eutrophication is often seen in fresh water lakes. The main causes of eutrophication in these water systems are sediments and thermal stratification, with agricultural runoff from fertilizers and manure, containing nitrates and phosphates and discharge of partially treated or untreated sewages or phosphate containing detergents.

Correct Option: B

Eutrophication is often seen in fresh water lakes. The main causes of eutrophication in these water systems are sediments and thermal stratification, with agricultural runoff from fertilizers and manure, containing nitrates and phosphates and discharge of partially treated or untreated sewages or phosphate containing detergents.