Which process does not result in the return of carbon dioxide to the atmosphere?

Options

A. Combustion of fossil fuels
B. Decomposition of humus
C. Respiration by bacteria
D. Photosynthesis by green plants

Answer

To solve the question "Which process does not result in the return of carbon dioxide to the atmosphere?", we will analyze each option provided in the question step by step.

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks for a process that does not release carbon dioxide back into the atmosphere.

2. **Analyzing the First Option - Combustion of Fossil Fuels**:
- Combustion of fossil fuels (like coal and petroleum) involves burning these fuels, which releases carbon dioxide as a byproduct.
- **Conclusion**: This process does result in the return of carbon dioxide to the atmosphere.

3. **Analyzing the Second Option - Decomposition of Humus**:
- Decomposition is the process where organic matter breaks down into simpler substances. During this process, carbon dioxide is released into the atmosphere as organic compounds are converted to inorganic forms.
- **Conclusion**: This process also results in the return of carbon dioxide to the atmosphere.

4. **Analyzing the Third Option - Restoration by Bacteria (Aerobic Respiration)**:
- Aerobic respiration by bacteria involves the breakdown of glucose in the presence of oxygen, producing carbon dioxide and water as byproducts.
- **Conclusion**: This process results in the return of carbon dioxide to the atmosphere.

5. **Analyzing the Fourth Option - Photosynthesis**:
- Photosynthesis is the process by which green plants convert carbon dioxide and sunlight into glucose and oxygen. During this process, carbon dioxide is taken from the atmosphere and used to produce glucose.
- **Conclusion**: This process does not release carbon dioxide; instead, it fixes carbon dioxide from the atmosphere.

6. **Final Conclusion**: Based on the analysis, the process that does not result in the return of carbon dioxide to the atmosphere is **Photosynthesis**.

### Answer:
The correct answer is **Photosynthesis** (Option 4).

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