Question

In which pollution zone of the river, the dissolved oxygen reduced to 0?

(a) Zone of degradation

(b) Zone of recovery

(c) Zone of clean water

(d) Zone of active decomposition

This question was posed to me in homework.

This interesting question is from Pollution Zones in River in portion Natural Methods of Wastewater Disposal of Environmental Engineering

Answer 1

Correct choice is (d) Zone of active decomposition

Easiest explanation: The dissolved oxygen, reduced to 0 in the zone of active decomposition. The water is highly polluted in this zone.