Circulation in Human is `:-`

Options

A. Single `&` Open
B. Double `&` Open
C. Double `&` Close
D. Single `&` Closed

Answer

### Step-by-Step Solution:

1. **Understanding Circulation Types**:
- Human circulation is classified as a closed type. This means that the blood circulates within a network of blood vessels and does not leave the system.
- Therefore, options indicating open circulation can be eliminated.

2. **Identifying Double Circulation**:
- Humans exhibit double circulation, which consists of two separate circuits: pulmonary circulation and systemic circulation.
- In pulmonary circulation, blood is transported from the heart to the lungs and back to the heart. This is where blood gets oxygenated.
- In systemic circulation, oxygenated blood is pumped from the heart to the rest of the body and returns deoxygenated blood back to the heart.

3. **Structure of the Heart**:
- The human heart is a four-chambered organ consisting of two atria (left and right) and two ventricles (left and right).
- Blood flow begins in the right atrium, where deoxygenated blood from the body enters via the inferior vena cava.
- From the right atrium, blood moves to the right ventricle, which pumps it into the pulmonary artery leading to the lungs.

4. **Oxygenation Process**:
- In the lungs, blood releases carbon dioxide and absorbs oxygen. This oxygenated blood then travels back to the heart via the pulmonary veins into the left atrium.

5. **Systemic Circulation**:
- From the left atrium, blood moves into the left ventricle, which then pumps the oxygenated blood into the aorta.
- The aorta distributes oxygen-rich blood to all parts of the body.

6. **Conclusion**:
- The two circuits (pulmonary and systemic) constitute the double circulation in humans, confirming that the correct answer to the question is "double circulation" and "closed circulation".

### Final Answer:
- The circulation in humans is classified as **double circulation** and **closed circulation**.