Assertion : Moment of inertia about an axis passing throught centre of mass is always minimum
Reason : Theorem of parallel axis can be applied for 2-D as well as 3-D bodies.

Options

A. If both Assertion and Reason are correct 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 fasle
D. If Assertion is false but Reason is true

Explanation

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

### Step 1: Understand the Assertion
The assertion states that the moment of inertia about an axis passing through the center of mass is always minimum. This is a fundamental principle in physics. The moment of inertia (I) is a measure of an object's resistance to changes in its rotation. When the axis of rotation is at the center of mass, the distribution of mass relative to that axis is such that the moment of inertia is minimized.

**Hint:** Recall the definition of moment of inertia and how it depends on the distribution of mass relative to the axis of rotation.

### Step 2: Understand the Reason
The reason states that the theorem of parallel axes can be applied for both 2-D and 3-D bodies. The parallel axis theorem states that the moment of inertia about any axis parallel to an axis through the center of mass can be calculated using the formula:
\[ I = I_{cm} + Md^2 \]
where \( I_{cm} \) is the moment of inertia about the center of mass, \( M \) is the mass of the body, and \( d \) is the distance between the two axes.

**Hint:** Think about how the parallel axis theorem is used to calculate moments of inertia for different axes and how it applies to both 2-D and 3-D objects.

### Step 3: Analyze the Relationship Between Assertion and Reason
While both the assertion and reason are true, the reason does not explain why the moment of inertia is minimum at the center of mass. The minimum moment of inertia at the center of mass is due to the nature of mass distribution, not merely because the parallel axis theorem applies to both 2-D and 3-D bodies.

**Hint:** Consider how the parallel axis theorem relates to the distribution of mass and how that affects the moment of inertia.

### Conclusion
Both the assertion and reason are true, but the reason is not the correct explanation for the assertion. Therefore, the correct answer to the question is that both statements are true, but the reason does not adequately explain the assertion.

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