A lower level of Dissolved Oxygen (DO) in water

1.Is bad for human consumption

2.May have been caused due to the presence of oxygen-demanding wastes

3.Threatens the fish and aquatic life

4.Cannot be used for irrigation purposes

5.May cause undesirable taste and odour

A1, 2 & 3 only

B1, 2 & 4 only

C2, 3 & 5 only ✓ Correct

D3, 4 & 5 only

Correct answer: (C) 2, 3 & 5 only

Explanation

Low dissolved oxygen usually signals that oxygen-demanding organic waste is being broken down by microbes in the water.

Statement 2: decay of such oxygen-demanding wastes consumes oxygen and lowers the level, a genuine cause.

Statement 3: fish and other aquatic life suffocate as oxygen falls, so their survival is threatened.

Statement 5: anaerobic decay releases gases that give the water undesirable taste and odour.

Statement 1 and Statement 4: low oxygen alone does not bar drinking or irrigation, so those are wrong.

Dissolved oxygen is a key indicator of a water body's health and self-purifying capacity.

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