Assertion `:-` In cortical nephrone, the loop of Henle is too short and extends only very little into medulla.
Reason `:-` Vasa recta is absent or highly reduced in cortical nephrons.

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 in cortical nephrons, the loop of Henle is short and extends only a little into the medulla.
- This is true because cortical nephrons are primarily located in the renal cortex and have shorter loops of Henle compared to juxtamedullary nephrons, which have longer loops that extend deep into the medulla.

2. **Understanding the Reason**:
- The reason provided states that the vasa recta is absent or highly reduced in cortical nephrons.
- This is also true. The vasa recta are the straight capillaries that supply blood to the medulla and are more prominent in juxtamedullary nephrons, which have longer loops of Henle. In cortical nephrons, the blood supply is mainly through peritubular capillaries, and the vasa recta is either absent or significantly reduced.

3. **Analyzing the Relationship**:
- The assertion and reason are both true statements about cortical nephrons.
- However, the reason does not directly explain the assertion. The short loop of Henle in cortical nephrons is a structural adaptation, while the presence or absence of vasa recta is more about the blood supply and does not influence the length of the loop of Henle.

4. **Conclusion**:
- Both the assertion and reason are true, but the reason does not support the assertion. Therefore, if the question asks whether the assertion is true and whether the reason is a correct explanation of the assertion, the answer would be that both are true, but the reason is not a correct explanation for the assertion.