The longest loop of Henle is found in

Options

A. Kangaroo rat
B. Opposum
C. Rhesus
D. monkey

Answer

To determine which animal has the longest loop of Henle, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Loop of Henle**: The loop of Henle is a U-shaped part of the nephron in the kidney, which plays a crucial role in the concentration of urine by reabsorbing water and salts.

2. **Identify the Animals in Question**: The options provided are kangaroo rat, opossum, and rhesus monkey.

3. **Research the Adaptations of Each Animal**:
- **Kangaroo Rat**: This animal is adapted to arid environments and has a long loop of Henle that allows it to produce highly concentrated urine, minimizing water loss.
- **Opossum**: Generally, opossums have shorter loops of Henle compared to kangaroo rats.
- **Rhesus Monkey**: Similar to opossums, rhesus monkeys do not have adaptations for extreme water conservation like the kangaroo rat.

4. **Conclude Based on Adaptations**: Since the kangaroo rat has evolved to survive in desert conditions, its long loop of Henle is an adaptation that allows it to conserve water effectively.

5. **Final Answer**: The longest loop of Henle is found in the **kangaroo rat**.