The maximum permissible limit for fluoride in drinking water is A. 0.1 mg/liter B. 1.5 mg/liter C. 5 mg/liter D. 10 mg/liter

Option A: 0.1 mg/liter is too low. This level of fluoride would not be effective in preventing tooth decay.

Option B: 1.5 mg/liter is the correct answer. This is the maximum permissible limit for fluoride in drinking water, as set by the WHO.

Option C: 5 mg/liter is too high. This level of fluoride can cause health problems, such as dental fluorosis.

Option D: 10 mg/liter is much too high. This level of fluoride can cause serious health problems, such as skeletal fluorosis, which is a condition that causes pain and stiffness in the bones.