`CO_(2)` is not a byproduct in

Options

A. Aerobic respiration in animals
B. Alcoholic fermentation
C. Lactate fermentation
D. Aerobic respiration in plants.

Answer

To determine in which reaction carbon dioxide (CO₂) is not a byproduct, we need to analyze the processes of aerobic respiration and fermentation.

### Step-by-Step Solution:

1. **Understanding Aerobic Respiration**:
- Aerobic respiration occurs in the presence of oxygen and involves several stages: glycolysis, the Krebs cycle, and the electron transport chain (ETC).
- In glycolysis, glucose is broken down into pyruvate, which occurs in the cytoplasm and does not produce CO₂.

2. **Krebs Cycle**:
- The pyruvate enters the mitochondria and is converted into acetyl-CoA, which then enters the Krebs cycle.
- During the Krebs cycle, carbon dioxide is released as a byproduct. For every molecule of glucose, approximately six molecules of CO₂ are produced.

3. **Electron Transport Chain (ETC)**:
- The ETC occurs on the inner mitochondrial membrane (cristae) and also produces CO₂ as a byproduct during the oxidation of glucose.

4. **Understanding Fermentation**:
- Fermentation is an anaerobic process (occurs without oxygen) and can take two main forms: alcoholic fermentation and lactic acid fermentation.
- In alcoholic fermentation, pyruvate is converted into ethanol and CO₂ is released as a byproduct.
- In lactic acid fermentation, pyruvate is converted into lactic acid without the release of CO₂.

5. **Conclusion**:
- Among the processes discussed, lactic acid fermentation is the only one that does not produce carbon dioxide as a byproduct. Therefore, the correct answer to the question is lactic acid fermentation.

### Final Answer:
CO₂ is not a byproduct in **lactic acid fermentation**.