Which of the following would have the same `O_(2)` content?

Options

A. Blood entering the lungs and blood leaving the lungs
B. Blood entering the right side of the heart and blood leaving the right side of the heart
C. Blood entering the right side of the heart and blood leaving the left side of the heart
D. Blood entering the tissue capillaries and blood leaving the tissue capillaries

Explanation

To determine which of the given options would have the same O₂ content, we need to analyze each option based on the principles of gas exchange in the human circulatory system.

### Step-by-Step Solution:

1. **Understand the Context of Oxygen Content**:
- Oxygen content in blood changes during gas exchange processes in the lungs and tissues. Blood that has not undergone gas exchange will have the same oxygen content.

2. **Evaluate Option 1**:
- **Blood entering the lungs and leaving the lungs**:
- Blood entering the lungs is deoxygenated and will gain oxygen during gas exchange. Blood leaving the lungs is oxygenated.
- **Conclusion**: The oxygen content is different. (This option is incorrect.)

3. **Evaluate Option 2**:
- **Blood entering the right side of the heart and blood leaving the right side of the heart**:
- Blood enters the right atrium from the body and moves to the right ventricle, then is pumped to the lungs. There is no gas exchange occurring in the right side of the heart.
- **Conclusion**: The oxygen content remains the same. (This option is correct.)

4. **Evaluate Option 3**:
- **Blood entering the right side of the heart and leaving the left side of the heart**:
- Blood enters the right atrium, goes to the right ventricle, then to the lungs for gas exchange, and finally enters the left atrium.
- **Conclusion**: The oxygen content is different due to gas exchange in the lungs. (This option is incorrect.)

5. **Evaluate Option 4**:
- **Blood entering tissue capillaries and leaving tissue capillaries**:
- Blood delivers oxygen to tissues and picks up carbon dioxide in the capillaries.
- **Conclusion**: The oxygen content is different due to gas exchange in tissues. (This option is incorrect.)

### Final Conclusion:
The only option that has the same O₂ content is **Option 2: Blood entering the right side of the heart and blood leaving the right side of the heart**.