Renal portal vein carries blood to

Options

A. Liver
B. Kidney
C. Heart directly
D. Brain

Explanation

**Step-by-Step Solution:**

1. **Understanding the Renal Portal Vein:**
- The renal portal vein is a specialized venous connection in certain animals, particularly amphibians like frogs. It plays a crucial role in the circulatory system.

2. **Circulatory System Overview:**
- Animals generally have two main types of circulatory systems: systemic and pulmonary. The systemic circulation connects the heart to the body tissues, while the pulmonary circulation connects the heart to the lungs.

3. **Specialization in Amphibians:**
- In amphibians, the circulatory system is adapted to their unique physiology. Frogs, for example, have a specialized connection that allows for efficient blood flow between the lower body and the kidneys.

4. **Function of the Renal Portal Vein:**
- The renal portal vein specifically carries blood from the lower body to the kidneys. This is where blood filtration occurs, and nitrogenous waste is eliminated.

5. **Outcome of Blood Filtration:**
- After the filtration process in the kidneys, the purified blood is then supplied to the rest of the body, ensuring that the organs receive clean and filtered blood.

6. **Conclusion:**
- Therefore, the renal portal vein carries blood to the kidneys, making option B the correct answer.

**Final Answer:** The renal portal vein carries blood to the **kidneys**.

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