Assertion :- (A) total number of octahedral voids present in unit cell of cubic close of each packing including the one that is present at the body centre . Is four .
Reason :- ( R) Besides the body centre there is one octahedral void present at the centre of each of the six faces of the unit cell and each of which is shared between two adjeccent units cells.

Options

A. Assertion and reason both are correct statements and Reason is correct explantion for Assertion .
B. Asserton and Reason both are correct statement but Reason is not correct explanation for assertion .
C. Assertion is correct statement but reason is worng statement .
D. Assertion is Wrong statement but Reason is correct statement .

Explanation

To solve the question, we need to analyze the assertion and the reason provided regarding the number of octahedral voids in a cubic close-packed (CCP) structure.

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that the total number of octahedral voids in a unit cell of cubic close packing, including the one at the body center, is 4.

2. **Analyzing the Octahedral Voids**:
- In a face-centered cubic (FCC) structure (which is the same as cubic close packing), there is 1 octahedral void located at the body center of the cube.
- Additionally, there are octahedral voids located at the edges of the cube.

3. **Counting the Edge Voids**:
- There are 12 edges in a cube. Each edge contributes an octahedral void that is shared between 4 adjacent unit cells.
- Therefore, the contribution of the edge voids is calculated as follows:
\[ \text{Number of edge voids} = \frac{12 \text{ edges} \times 1 \text{ void per edge}}{4} = 3 \text{ voids} \]

4. **Total Octahedral Voids**:
- Adding the void at the body center (1 void) to the edge voids (3 voids):
\[ \text{Total octahedral voids} = 1 \text{ (body center)} + 3 \text{ (from edges)} = 4 \text{ voids} \]

5. **Verifying the Reason**:
- The reason states that there is one octahedral void at the center of each of the six faces of the unit cell, which is incorrect. The octahedral voids are actually located at the body center and shared among the edges, not at the faces.
- The correct statement should focus on the voids at the edges and the body center.

6. **Conclusion**:
- The assertion is correct: there are indeed 4 octahedral voids in a cubic close-packed unit cell.
- The reason is incorrect as it misstates the location of the octahedral voids.

### Final Answer:
- The assertion is true, but the reason is false.