Assertion : The ability of a material to permit the passage of magnetic lines of force through it is called magnetic permeability.
Reason: For a perfect diamagnetic substance, permeability is always one.

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

Explanation

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

### Step 1: Understand the Assertion
The assertion states that "The ability of a material to permit the passage of magnetic lines of force through it is called magnetic permeability."

**Analysis**:
- This statement is true. Magnetic permeability (μ) is indeed defined as the measure of how easily a magnetic field can penetrate a material.

### Step 2: Understand the Reason
The reason states that "For a perfect diamagnetic substance, permeability is always one."

**Analysis**:
- This statement is false. A perfect diamagnetic material has a relative permeability (μ_r) of less than 1, specifically it is equal to 0. This means that it completely expels magnetic fields.

### Step 3: Conclusion
- Since the assertion is true and the reason is false, we conclude that the overall statement is that the assertion is true, but the reason is false.

### Final Answer
- Assertion is true, but the reason is false.