Amount of Residual Chlorine in Public Water Supply

The amount of residual chlorine left in public water supply for safety against pathogenic bacteria is about 0.05 to 0.5 ppm.

This is the amount of chlorine that is left after the water has been treated and chlorinated. The chlorine helps to kill harmful bacteria and viruses, making the water safe to drink.

The answer is b) 0.05 to 0.5 ppm.