The water pollution in river is measured by the dissolved amount of
- AChlorine
- BOzone
- CNitrogen
- DOxygenCorrect
Explanation
The correct answer is D because the health of a river is primarily assessed through its Biological Oxygen Demand or BOD. Aquatic organisms like fish and aerobic bacteria need dissolved oxygen to survive. When a river is polluted with organic waste, microorganisms consume large amounts of oxygen to decompose that waste. Therefore, a low level of dissolved oxygen indicates high pollution, while a high level indicates cleaner water. This measurement is the standard scientific method used to determine the quality of river water.
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