A : The number of spheres are equal to the number of octahedral voids as well as tetrahedral void.
R : Octahedral void and tetrahedral void has equal size.

Options

A. If both Assertion & Reason are true and the reason is the correct explanation of the assertion then mark (1)
B. If both Assertion & Reason are true but the reason is not the correct explanation of the assertion, then mark (2)
C. If Assertion is true statement but Reason is false then mark (3)
D. If both Assertion and Reason are false statements, then mark (4)

Answer

To solve the question, we need to analyze both the assertion (A) and the reason (R) provided in the statement.

### Step-by-Step Solution:

1. **Understanding the Assertion (A)**:
- The assertion states that the number of spheres (atoms) is equal to the number of octahedral voids as well as the number of tetrahedral voids.
- In a crystal lattice, the number of octahedral voids is equal to the number of atoms (Z) present in the unit cell.
- However, the number of tetrahedral voids is twice the number of atoms in the unit cell, which means it is equal to 2Z.

2. **Analyzing the Assertion**:
- If we assume Z = 10 (as an example), then:
- Number of octahedral voids = Z = 10
- Number of tetrahedral voids = 2Z = 20
- Therefore, the assertion that the number of spheres is equal to the number of octahedral voids and tetrahedral voids is **false**.

3. **Understanding the Reason (R)**:
- The reason states that octahedral voids and tetrahedral voids have equal size.
- To evaluate this, we need to look at the radius ratio for both types of voids:
- The radius ratio for tetrahedral voids lies between 0.225 and 0.414.
- The radius ratio for octahedral voids lies between 0.414 and 0.732.

4. **Analyzing the Reason**:
- Since the radius ratios for tetrahedral and octahedral voids are different, it indicates that the sizes of these voids are also different.
- Thus, the reason that octahedral voids and tetrahedral voids have equal size is **false**.

5. **Conclusion**:
- Both the assertion (A) and the reason (R) are false.
- Therefore, the correct answer is that both the assertion and reason are false.

### Final Answer:
Both assertion (A) and reason (R) are false.