The correct answer is: B. 0.05 to 0.5 ppm.
Chlorine is a disinfectant that is used to kill harmful bacteria in drinking water. The amount of chlorine that is left in the water after treatment is called the residual chlorine. The residual chlorine level should be between 0.05 and 0.5 parts per million (ppm) to ensure that the water is safe to drink.
If the residual chlorine level is too low, there is a risk that harmful bacteria will not be killed and could make people sick. If the residual chlorine level is too high, it can cause irritation to the skin and eyes.
The amount of chlorine that is needed to disinfect water depends on a number of factors, including the type of bacteria that are present, the pH of the water, and the temperature of the water. The chlorine level should be monitored regularly to ensure that it is within the safe range.
Here is a brief explanation of each option:
- Option A: 0.01 to 0.05 ppm. This is a very low level of chlorine and is not likely to be effective in killing harmful bacteria.
- Option B: 0.05 to 0.5 ppm. This is the recommended level of chlorine for drinking water.
- Option C: 0.5 to 1.0 ppm. This is a higher level of chlorine that may be necessary to disinfect water that is contaminated with a large number of harmful bacteria.
- Option D: 1.0 to 5.0 ppm. This is a very high level of chlorine that can be irritating to the skin and eyes.