Assertion (A) : The size of a cation is larger in `TV` than in `OV`.
Reason (R ) : Cations occupy more space than anions is crystals packing.

Options

A. If both `(A)` and `(R)` are correct, and `(R)` is the correct explanation of `(A)`
B. If both `(A)` and `(R)` are correct, but `(R)` is not the correct explanation of `(A)`
C. If `(A)` is correct, but `(R)` is incorrect.
D. If both `(A)` and `(R)` are incorrect.

Explanation

To solve the question regarding the assertion and reason provided, we will analyze each statement step by step.

### Step-by-Step Solution:

1. **Understanding the Assertion (A)**:
- The assertion states that the size of a cation is larger in tetrahedral voids (TV) than in octahedral voids (OV).
- In crystal structures, cations can occupy different types of voids. The size of the cation that can fit into these voids is determined by the radius ratio of cations to anions.

2. **Radius Ratio for Tetrahedral and Octahedral Voids**:
- For tetrahedral voids, the radius ratio (r⁺/r⁻) ranges from 0.225 to 0.414.
- For octahedral voids, the radius ratio (r⁺/r⁻) ranges from 0.414 to 0.732.
- This indicates that the size of cations that can fit into octahedral voids is larger than those that can fit into tetrahedral voids.

3. **Conclusion on the Assertion**:
- Since the size of cations in octahedral voids is larger than in tetrahedral voids, the assertion (A) is **false**.

4. **Understanding the Reason (R)**:
- The reason states that cations occupy more space than anions in crystal packing.
- However, it is known that cations are generally smaller than anions due to their positive charge, which pulls the electron cloud closer to the nucleus.

5. **Conclusion on the Reason**:
- Since cations are smaller than anions, the statement in the reason (R) is also **false**.

6. **Final Conclusion**:
- Both the assertion (A) and the reason (R) are incorrect. Therefore, the correct answer is option D: both A and R are incorrect.