Why is the BOD of untreated sewage of a city more than that of a river polluted by industrial wastes?

Explanation

**Step-by-Step Solution:**

1. **Understanding BOD**:
- BOD stands for Biochemical Oxygen Demand. It measures the amount of oxygen that microorganisms require to decompose organic matter in water.

2. **Organic Matter in Sewage**:
- Untreated sewage from a city contains a high amount of organic waste. This includes human waste, food scraps, and other biodegradable materials.

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