Assertion :- When a cell or tissue is placed in an isotonic solution, there is no net flow of water towards the inside or outside.
Reason:- In isotonic solution net volume of cell remains constant.

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

Answer

To analyze the given assertion and reason, we will break down the statements and evaluate their accuracy step by step.

### Step 1: Understand the Assertion
The assertion states: "When a cell or tissue is placed in an isotonic solution, there is no net flow of water towards the inside or outside."

- **Explanation**: An isotonic solution has the same solute concentration as the inside of the cell. Therefore, the movement of water into the cell is equal to the movement of water out of the cell. This results in no net movement of water, meaning the cell remains in equilibrium.

### Step 2: Understand the Reason
The reason states: "In isotonic solution, the net volume of the cell remains constant."

- **Explanation**: Since there is no net movement of water, the volume of the cell does not change. It remains constant because the rates of water entering and leaving the cell are equal.

### Step 3: Evaluate the Relationship Between Assertion and Reason
Now, we need to determine if the reason provided is the correct explanation for the assertion.

- While both statements are true, the reason does not directly explain why there is no net flow of water. The reason states that the volume remains constant, but it does not clarify that this is due to equal solute concentrations inside and outside the cell.

### Conclusion
Based on the analysis:
- Both the assertion and reason are true.
- However, the reason is not the correct explanation for the assertion.

### Final Answer
The correct option is: **Assertion and reason are true, but the reason is not the correct explanation of the assertion.**

---