The question consist of two statements each, printed as Assertion and Reason. While answering these questions you are required to choose any one of the following four responses:
Assertion: Co-ordination number of cobalt in the complex `[Co(en)_3]^(3+)` is six.
Reason: Ethylenediamine acts as a bidentate ligand.

Options

A. Statement-1 is True, Statement-2 is True, Statement-2 is a correct explanation for Statement-1
B. Statement-1 is True, Statement-2 is True, Statement-2 is NOT a correct explanation for Statement-1
C. Statement-1 is True, Statement-2 is False.
D. Statement-1 is False, Statement-2 is True.

Explanation

To solve the question, we will analyze both the Assertion and the Reason provided.

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that the coordination number of cobalt in the complex \([Co(en)_3]^{3+}\) is six.
- The coordination number is defined as the number of ligand atoms that are bonded to the central metal ion.

2. **Analyzing the Ligand**:
- The ligand in question is ethylenediamine (en), which is a bidentate ligand.
- A bidentate ligand can attach to a metal ion at two points, meaning it can form two bonds with the metal.

3. **Counting the Ligands**:
- In the complex \([Co(en)_3]^{3+}\), there are three ethylenediamine ligands.
- Since each ethylenediamine ligand can form two bonds with the cobalt ion, the total number of bonds formed is:
\[ 3 \text{ (ligands)} \times 2 \text{ (bonds per ligand)} = 6 \text{ bonds} \]
- Therefore, the coordination number of cobalt in this complex is indeed 6.

4. **Understanding the Reason**:
- The reason states that ethylenediamine acts as a bidentate ligand.
- This is a correct statement because ethylenediamine has two nitrogen atoms that can donate lone pairs to the metal ion, allowing it to bind at two sites.

5. **Conclusion**:
- Both the assertion and the reason are true.
- Furthermore, the reason provides a correct explanation for the assertion, as it describes how ethylenediamine contributes to the coordination number of cobalt.

### Final Answer:
- The correct response is:
- Both the assertion and the reason are true, and the reason is the correct explanation of the assertion.