Assertion : The weight of the atmosphere exerts a pressure on the surface of earth.
Reason : When we go upwards, the magnitude of atmospheric pressure decrease gradually.

Options

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

Answer

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

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that "The weight of the atmosphere exerts a pressure on the surface of the Earth."
- This is true because the atmosphere is made up of air, which has weight. The weight of the air above us creates atmospheric pressure on the surface of the Earth.

2. **Understanding the Reason**:
- The reason states that "When we go upwards, the magnitude of atmospheric pressure decreases gradually."
- This is also true. As we ascend (for example, climbing a mountain or going up in an airplane), we move away from the bulk of the atmosphere, which results in a decrease in atmospheric pressure.

3. **Analyzing the Relationship**:
- The assertion is true, and the reason is also true. However, we need to determine if the reason is the correct explanation of the assertion.
- The assertion explains that atmospheric pressure is due to the weight of the atmosphere, while the reason explains how atmospheric pressure changes with altitude.

4. **Conclusion**:
- Since both the assertion and the reason are true, but the reason does not directly explain why the weight of the atmosphere exerts pressure, we conclude that the correct answer is:
- **Option 2: Both assertion and reason are true, but the reason is not the correct explanation of the assertion.**

### Final Answer:
**Option 2: Both assertion and reason are true, but reason is not the correct explanation of assertion.**

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