Fish die in water bodies polluted by sewage due to: — Qualitative and Quantitative Analysis Chemistry Question

💡 Solution & Explanation

Step 1: Sewage contains large quantities of organic waste, which increases the nutrient load in water bodies. Step 2: Aerobic bacteria decompose this organic matter and rapidly multiply, consuming the dissolved oxygen in the water. Step 3: This depletion of dissolved oxygen (high Biochemical Oxygen Demand) deprives fish of the oxygen necessary for respiration, causing them to suffocate and die, corresponding to option (b).