[A]: The nitrogen content of the plant cannot be detected accurately by ash analysis.
[R]: On burning of plant, nitrogen component is given off as `NH_3` & other gases

Options

A. If both A and R are true and R is the correct explanation of A
B. If both A and R are true but R is not the correct explanation of A
C. If A is true and R is false
D. If both A and R are false

Answer

To solve the assertion and reason question, we need to analyze both statements carefully.

### Step-by-Step Solution:

1. **Understanding Ash Analysis**:
- Ash analysis is a method used to determine the inorganic mineral content of a plant sample. This process involves burning the plant material, which incinerates the organic compounds and leaves behind inorganic minerals.

2. **Evaluating the Assertion**:
- The assertion states that "the nitrogen content of the plant cannot be detected accurately by ash analysis." This is true because during the ash analysis process, nitrogen is released in the form of gases (like nitrogen gas and ammonia) when the plant is burned. Therefore, the nitrogen content cannot be accurately measured since it escapes into the atmosphere.

3. **Evaluating the Reason**:
- The reason states that "on burning of the plant, the nitrogen component is given off as NH₃ and other gases." This is also true. When the plant is burned, nitrogen is released as ammonia (NH₃) and other nitrogenous gases, which confirms that the nitrogen is not retained in the ash.

4. **Determining the Relationship**:
- Since both the assertion and the reason are true, and the reason correctly explains why the assertion is true, we conclude that both statements are valid and the reason provides a correct explanation for the assertion.

5. **Final Conclusion**:
- Therefore, the correct answer is that both the assertion and reason are true, and the reason is a correct explanation of the assertion.

### Final Answer:
Both assertion and reason are true, and the reason is the correct explanation for the assertion.

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