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 cortex of the kidney, and their loops of Henle do not penetrate deeply into the medulla.

2. **Understanding the Reason**: The reason provided states that vasa recta is absent or highly reduced in cortical nephrons. This is also true. Vasa recta, which are the straight capillaries that supply blood to the medulla, are indeed absent or significantly reduced in cortical nephrons.

3. **Analyzing the Relationship**: While both the assertion and reason are true, we need to determine if the reason explains the assertion. The assertion describes the structural characteristics of cortical nephrons, while the reason discusses the presence of vasa recta. The absence of vasa recta does not explain why the loop of Henle is short in cortical nephrons.

4. **Conclusion**: Therefore, both the assertion and the reason are true, but the reason is not a correct explanation for the assertion.

### Final Answer:
- Assertion: True
- Reason: True
- Explanation: The reason does not explain the assertion.