Balance between `CO_(2)` and `O_(2)` is maintained by

Options

A. Transpiration
B. Photosynthesis
C. Photorespiration
D. `C_(4)` pathway.

Answer

To answer the question regarding how the balance between carbon dioxide (CO₂) and oxygen (O₂) is maintained, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Processes**:
- Photosynthesis and respiration are the two main biological processes that involve the exchange of CO₂ and O₂.
- Photosynthesis occurs in plants, where they convert CO₂ and sunlight into glucose and O₂.
- Respiration occurs in animals (including humans), where they consume O₂ and produce CO₂.

2. **Role of Photosynthesis**:
- During photosynthesis, plants absorb CO₂ from the atmosphere and release O₂ as a byproduct. This process is essential for maintaining the balance of gases in the environment.
- The overall equation for photosynthesis can be summarized as:
\[ 6CO_2 + 6H_2O + light \ energy \rightarrow C_6H_{12}O_6 + 6O_2 \]
- This shows that for every six molecules of CO₂ used, six molecules of O₂ are released.

3. **Role of Respiration**:
- In contrast, during respiration, organisms take in O₂ and release CO₂. The equation for respiration is:
\[ C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + energy \]
- This process helps to utilize the O₂ produced by plants and returns CO₂ back to the atmosphere.

4. **Evaluating the Options**:
- **Transpiration**: This is the process of water vapor loss from plants and does not directly affect the balance of CO₂ and O₂. Thus, it is incorrect.
- **Photosynthesis**: This process directly contributes to the balance by consuming CO₂ and producing O₂. Therefore, it is the correct answer.
- **Photorespiration**: This is a wasteful process that occurs when the enzyme RuBisCO fixes O₂ instead of CO₂, leading to a net loss of fixed carbon and is not a significant contributor to the balance. Hence, it is incorrect.
- **C4 Pathway**: This is a specific adaptation in some plants to efficiently fix CO₂, but it does not directly maintain the overall balance of CO₂ and O₂ in the atmosphere. Thus, it is also incorrect.

5. **Conclusion**:
- The process that maintains the balance between CO₂ and O₂ in the environment is **photosynthesis**.

### Final Answer:
The balance between CO₂ and O₂ is maintained by **photosynthesis**.