Assertion : BOD indicates the extent of water pollution by organic wastes.
Reason: Increase in BOD decrease dissolved oxygen of waste water.

Options

A. If both Assertion and Reason are true and Reason is a correct explanation of Assertion.
B. If both Assertion and Reason are true but Reason is not a correct explanation of Assertion
C. It Assertion and true but Reason is false.
D. If both Assertion and Reason are false.

Answer

### Step-by-Step Solution:

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

2. **Assertion Analysis**:
- The assertion states that "BOD indicates the extent of water pollution by organic wastes." This is true because a high BOD value signifies a high level of organic pollution in the water, indicating that there is a significant amount of organic material that needs to be decomposed by microorganisms.

3. **Reason Analysis**:
- The reason states that "Increase in BOD decreases dissolved oxygen of wastewater." This is also true. When the BOD increases, it means that there is more organic matter present, which requires more oxygen for decomposition. As microorganisms consume this oxygen, the amount of dissolved oxygen in the water decreases.

4. **Conclusion**:
- Both the assertion and the reason are true. Furthermore, the reason correctly explains the assertion. Therefore, we can conclude that the assertion is correct, and the reason is also correct and provides a valid explanation for the assertion.

### Final Answer:
Both the assertion and reason are true, and the reason correctly explains the assertion.

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