Assertion (A) : Graphite is an example of tetragonal crystal system.
Reason (R ) : For a tetragonal system, `a = b != c` and `alpha = beta = 90^(@), gamma = 120^(@)`.

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, we need to analyze both the assertion and the reason provided.

### Step-by-Step Solution:

1. **Understanding the Assertion (A)**:
- The assertion states that "Graphite is an example of tetragonal crystal system."
- To evaluate this, we need to know the crystal structure of graphite. Graphite is actually classified as a hexagonal crystal system, not tetragonal. Therefore, the assertion is **false**.

2. **Understanding the Reason (R)**:
- The reason states the conditions for a tetragonal crystal system: "For a tetragonal system, a = b ≠ c and α = β = 90°, γ = 120°."
- The correct conditions for a tetragonal system are:
- a = b (the lengths of the two axes are equal)
- c (the length of the third axis) is different from a and b
- α = β = γ = 90° (the angles between the axes are all 90 degrees).
- The statement incorrectly mentions that γ = 120°, which is not true for a tetragonal system. Therefore, the reason is also **false**.

3. **Conclusion**:
- Since both the assertion and the reason are false, the correct answer is that both A and R are incorrect.

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