Alcoholic fermentation is brought about by the action of

Options

A. `CO_2`
B. `O_2`
C. Invertase
D. Yeast

Answer

To solve the question "Alcoholic fermentation is brought about by the action of," we need to analyze the process of alcoholic fermentation and identify the key components involved.

### Step-by-Step Solution:

1. **Understanding Alcoholic Fermentation**:
- Alcoholic fermentation is a biological process where sugars are converted into alcohol (ethanol) and carbon dioxide (CO2). This process is primarily used in the production of alcoholic beverages and in baking.

2. **Identifying the Key Organism**:
- The primary organism responsible for alcoholic fermentation is yeast. Yeast is a type of fungus that can metabolize sugars anaerobically (without oxygen) to produce ethanol and CO2.

3. **Role of Yeast**:
- Yeast contains enzymes, such as zymase, that facilitate the conversion of glucose into ethanol and CO2. This process occurs in the absence of oxygen, making it an anaerobic fermentation.

4. **Eliminating Other Options**:
- CO2 and O2 are byproducts or conditions of the fermentation process but are not the agents that cause fermentation. Invertase is an enzyme that helps break down sucrose into glucose and fructose but is not the main agent of fermentation itself.

5. **Conclusion**:
- Therefore, the correct answer to the question is that alcoholic fermentation is brought about by the action of yeast.

### Final Answer:
Alcoholic fermentation is brought about by the action of **yeast**.

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