The renal portal system of vertebrates is significant for

Options

A. Elimination of excess fats by kidneys
B. Removing nitrogenous wastes in kidneys
C. Supplying food to the kidneys
D. Draining blood from the kidney

Answer

### Step-by-Step Solution:

1. **Understanding the Renal Portal System**:
- The renal portal system is a specialized network of veins that collect blood from the posterior part of the body and the legs. This blood is directed towards the kidneys rather than the heart.

2. **Function of the Renal Portal System**:
- Once the blood reaches the kidneys, it is divided into capillaries. In these capillaries, the kidneys perform their primary function of filtering the blood.

3. **Role of the Kidneys**:
- The kidneys are responsible for removing nitrogenous waste products from the blood. This includes substances like urea, creatinine, and uric acid.

4. **Analyzing the Options**:
- **Option A**: Elimination of excess fats by kidneys - This is incorrect as the kidneys do not primarily eliminate fats.
- **Option B**: Removing nitrogenous waste in kidneys - This is correct as it accurately describes a key function of the renal portal system.
- **Option C**: Supplying food to the kidneys - This is misleading; while the kidneys receive blood, they do not primarily receive food.
- **Option D**: Draining blood from the kidneys - This is incorrect as the renal portal system is about supplying blood to the kidneys, not draining it.

5. **Conclusion**:
- The renal portal system of vertebrates is significant for **removing nitrogenous waste in kidneys** (Option B).