A : For an isolated system `Delta G = - TDeltaS_("total")`
R: For an isolated system q = 0.

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 and 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 is true statement but Reason is false, then mark (3)

Answer

To solve the question, we need to analyze the assertion and the reason provided, and determine their validity and relationship.

### Step-by-Step Solution:

1. **Understanding the Assertion (A)**:
- The assertion states: For an isolated system, \(\Delta G = -T \Delta S_{\text{total}}\).
- In thermodynamics, for an isolated system, the total change in Gibbs free energy (\(\Delta G\)) is related to the total entropy change (\(\Delta S_{\text{total}}\)) of the system. This relationship holds true because, in an isolated system, energy and matter cannot be exchanged with the surroundings.

2. **Understanding the Reason (R)**:
- The reason states: For an isolated system, \(q = 0\).
- An isolated system is defined as one that does not exchange heat (\(q\)) or work (\(W\)) with its surroundings. Therefore, it is correct to say that \(q = 0\) in an isolated system.

3. **Analyzing the Relationship**:
- The assertion is true because it correctly describes the relationship between Gibbs free energy and entropy in an isolated system.
- The reason is also true because it accurately describes a characteristic of isolated systems.
- However, the reason does not directly explain why the assertion is true. The assertion is a consequence of the definitions and relationships in thermodynamics, while the reason simply states a property of isolated systems.

4. **Conclusion**:
- Both the assertion and reason are true, but the reason does not provide a correct explanation for the assertion. Therefore, the correct choice is that both are true, but the reason is not a correct explanation of the assertion.

### Final Answer:
- The correct answer is: **Option B**: Both assertion and reason are true, but reason is incorrect explanation of assertion.