The correct answer is C. 5 ppm.
Dissolved oxygen (DO) is the amount of oxygen that is dissolved in water. It is essential for the survival of fish and other aquatic life. The minimum DO concentration required for the survival of fish varies depending on the species of fish, the temperature of the water, and the presence of other pollutants. In general, a DO concentration of 5 ppm is considered to be the minimum required for the survival of most fish species.
Option A is incorrect because 3 ppm is below the minimum DO concentration required for the survival of most fish species. Option B is incorrect because 4 ppm is below the minimum DO concentration required for the survival of most fish species. Option D is incorrect because 10 ppm is above the minimum DO concentration required for the survival of most fish species.
It is important to note that the minimum DO concentration required for the survival of fish can vary depending on the specific conditions of the water body. For example, fish may require a higher DO concentration in cold water than in warm water. Additionally, fish may require a higher DO concentration in water that is polluted with other chemicals.