Which of the following are used as disinfectants during water treatment?

1.Chlorine

2.Phosphorus

3.Ozone

4.Nitrogen

5.Ultraviolet rays

A1, 2 & 3 only

B1, 2 & 4 only

C1, 3 & 5 only ✓ Correct

D2, 4 & 5 only

Correct answer: (C) 1, 3 & 5 only

Explanation

Chlorine, ozone and ultraviolet rays are used as disinfectants in water treatment.

Statement 1 is right, as chlorine is the most widely used water disinfectant.

Statement 3 is right, as ozone strongly oxidises and kills microorganisms.

Statement 5 is right, as ultraviolet rays inactivate pathogens without adding chemicals.

Statement 2 is wrong, since phosphorus is a nutrient, not a disinfectant.

Statement 4 is wrong, since nitrogen is not used to disinfect drinking water.

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