Assertion `:-` Proximal convoluted tubule is lined by brush-bordered cuboidal epithelium.
Reason `:-` PCT is main site of selective reabsorption of useful material from nephric filtrate.

Options

A. If both Assertion & Reason are True & the Reason is a correct explanation of the Assertion .
B. If both Assertion & Reason are True but Reason is not a correct explanation of the Assertion
C. If Assertion is True but the Reason is False.
D. If both Assertion & Reason are false.

Answer

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that the proximal convoluted tubule (PCT) is lined by brush-bordered cuboidal epithelium.
- This statement is **true** because the PCT is indeed lined with cuboidal epithelial cells that have microvilli, which give it a brush-like appearance.

2. **Understanding the Reason**:
- The reason provided states that the PCT is the main site of selective reabsorption of useful materials from nephric filtrate.
- This statement is also **true** because the PCT is responsible for reabsorbing a significant amount of water, nutrients, electrolytes, and small proteins from the filtrate.

3. **Analyzing the Relationship**:
- While both the assertion and reason are true, we need to evaluate if the reason correctly explains the assertion.
- The presence of brush-border cuboidal epithelium (assertion) does enhance the reabsorption process (reason) due to increased surface area. However, the reason does not specifically explain why the PCT is lined with this type of epithelium.

4. **Conclusion**:
- Since both statements are true but the reason does not adequately explain the assertion, we conclude that the correct answer is that both the assertion and reason are true, but the reason is not the correct explanation for the assertion.

### Final Answer:
- **Both the assertion and reason are true, but the reason is not the correct explanation for the assertion.**