Assertion : The complex `K_(3) [Cr(C_(2)O_(4))_(3)]` when present in aqueous solution , will give test for `K^(+)` , `Cr^(3+)` and oxalate ions .
Reason : The complex `K_(3) [Cr(C_(2)O_(4))_(3)]` will dissociate completely in solution .

Options

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

Explanation

To solve the given question, we need to analyze both the assertion and the reason provided.

### Step-by-Step Solution:

1. **Understanding the Assertion**:
The assertion states that the complex \( K_3[Cr(C_2O_4)_3] \) when present in aqueous solution will give tests for \( K^+ \), \( Cr^{3+} \), and oxalate ions.

2. **Analyzing the Complex**:
The complex \( K_3[Cr(C_2O_4)_3] \) consists of potassium ions \( K^+ \) and the coordination complex \( [Cr(C_2O_4)_3]^{3-} \).

3. **Dissociation in Aqueous Solution**:
When \( K_3[Cr(C_2O_4)_3] \) is dissolved in water, it dissociates into its constituent ions:
\[ K_3[Cr(C_2O_4)_3] \rightarrow 3K^+ + [Cr(C_2O_4)_3]^{3-} \]
Here, \( [Cr(C_2O_4)_3]^{3-} \) remains as a complex ion and does not dissociate further into \( Cr^{3+} \) and oxalate ions \( C_2O_4^{2-} \).

4. **Conclusion about the Assertion**:
The assertion is incorrect because while \( K^+ \) ions are released, \( Cr^{3+} \) ions and free oxalate ions are not produced. Instead, the complex ion \( [Cr(C_2O_4)_3]^{3-} \) remains intact.

5. **Understanding the Reason**:
The reason states that the complex \( K_3[Cr(C_2O_4)_3] \) will dissociate completely in solution.

6. **Analyzing the Reason**:
Coordination complexes do not dissociate completely; they dissociate partially. In this case, \( K_3[Cr(C_2O_4)_3] \) dissociates to give \( 3K^+ \) and the intact complex \( [Cr(C_2O_4)_3]^{3-} \).

7. **Conclusion about the Reason**:
The reason is also incorrect because it implies complete dissociation, which does not occur with coordination complexes.

8. **Final Conclusion**:
Both the assertion and the reason are incorrect. Therefore, the correct option for this question is option B.