The correct answer is C. 10 to 15 days.
Oxidation ponds are a type of wastewater treatment system that uses natural processes to remove pollutants from wastewater. The detention period is the amount of time that wastewater stays in the pond. The detention period for oxidation ponds is usually kept as 10 to 15 days. This allows enough time for the natural processes to remove the pollutants from the wastewater.
Option A is incorrect because the detention period for oxidation ponds is usually kept as 10 to 15 days, not 48 hours.
Option B is incorrect because the detention period for oxidation ponds is usually kept as 10 to 15 days, not 24 hours.
Option D is incorrect because the detention period for oxidation ponds is usually kept as 10 to 15 days, not 3 months.