BOD is

Options

A. amount of `O_(2)` required by a few bacteria in water
B. amount of `O_(2)` required by microbes for decomposition of organic matter
C. amount of `O_(2)` present in water at `37^(@)C`
D. all of the above

Answer

**Step-by-Step Solution:**

1. **Understanding BOD**: BOD stands for Biochemical Oxygen Demand. It is a measure of the amount of dissolved oxygen that aerobic microorganisms will consume while decomposing organic matter in water.

2. **Definition of BOD**: The BOD is defined as the amount of dissolved oxygen required by aerobic microorganisms to break down organic matter in a water sample over a specified time and at a certain temperature.

3. **Purpose of BOD**: BOD is an important indicator of water pollution. A high BOD indicates that a large amount of organic matter is present in the water, which means that the water is likely polluted.

4. **Analyzing the Options**:
- **Option A**: "Amount of oxygen required by a few bacteria in water" - This is incorrect because BOD refers to the oxygen required by aerobic microorganisms in general, not just a few bacteria.
- **Option B**: "Amount of oxygen required by microbes for decomposition of organic matter" - This is correct as it accurately describes what BOD measures.
- **Option C**: "Amount of oxygen present in water" - This is incorrect because BOD specifically measures the oxygen demand, not the amount of oxygen present.
- **Option D**: "All of the above" - This is incorrect since not all previous statements are true.

5. **Conclusion**: The correct answer is **Option B**: "Amount of oxygen required by microbes for decomposition of organic matter."

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