Assertion: Complex anion `[Re_(2)Cl_(8)]^(2-)` has one `delta`-bond, one sigma and two `pi`-bond.
Reason:` d_(z^(2))` orbital can never form `delta`-bond.

Options

A. If assertion is true but the reason is false
B. If assertion is false but reason is true
C. If both assertion and reason are true and the reason is the correct explanation of assertion
D. If both assertion and reason are true but reason is not the correct explanation of assertion

Explanation

To analyze the given assertion and reason statements regarding the complex anion \([Re_2Cl_8]^{2-}\), we can break down the solution into several steps:

### Step 1: Analyze the Assertion
The assertion states that the complex anion \([Re_2Cl_8]^{2-}\) has one delta bond, one sigma bond, and two pi bonds.

- **Understanding the bonding in \([Re_2Cl_8]^{2-}\)**:
- The complex consists of two rhenium (Re) atoms and eight chloride (Cl) ligands.
- Each Re atom is coordinated by four Cl ligands.
- The bonding involves:
- **One sigma bond**: This is formed by the head-on overlap of orbitals.
- **Two pi bonds**: These are formed by the side-on overlap of orbitals.
- **One delta bond**: This bond is formed by the overlap of d orbitals that have four lobes.

Thus, the assertion is **true**.

### Step 2: Analyze the Reason
The reason states that the \(d_{z^2}\) orbital can never form a delta bond.

- **Understanding the \(d_{z^2}\) orbital**:
- The \(d_{z^2}\) orbital has a distinct shape with two lobes along the z-axis and a donut-shaped ring around the center.
- Delta bonds are formed by orbitals that have four lobes, which is not the case for \(d_{z^2}\).

Therefore, the reason is also **true**.

### Step 3: Determine the Relationship
Now we need to determine if the reason correctly explains the assertion.

- While both statements are true, the reason does not explain why \([Re_2Cl_8]^{2-}\) has one delta bond, one sigma bond, and two pi bonds. The presence of a delta bond in the complex is due to the overall bonding configuration and the types of orbitals involved, not solely because \(d_{z^2}\) cannot form a delta bond.

### Conclusion
Both the assertion and reason are true, but the reason does not provide a correct explanation for the assertion.

Thus, the final answer is:
**Both assertion and reason are true, but the reason is not the correct explanation of the assertion.**