Big holes in Swiss cheese are made by

Options

A. a machine
B. a bacterium that produces methane gas
C. a bacterium producing a large amount of carbon dioxide
D. a fungus that releases a lot of gases during its metabolic activities

Explanation

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks about the formation of big holes in Swiss cheese. It is essential to identify the correct biological process or organism responsible for this phenomenon.

2. **Analyzing the Options**:
- **Option A**: Suggests that the holes are made by a machine. This is incorrect as Swiss cheese is a natural product.
- **Option B**: States that a bacterium produces methane gas. While some bacteria produce methane, it is not responsible for the holes in Swiss cheese.
- **Option C**: Indicates that a bacterium produces a large amount of carbon dioxide. This is a plausible option as carbon dioxide is known to create holes in cheese.
- **Option D**: Mentions a fungus that releases gas. While fungi can produce gases, they are not the primary cause of holes in Swiss cheese.

3. **Identifying the Correct Bacterium**: The bacterium responsible for producing carbon dioxide in Swiss cheese is **Propionibacterium shermani**. This bacterium ferments lactic acid and produces carbon dioxide as a byproduct, which leads to the formation of holes.

4. **Conclusion**: Based on the analysis, the correct answer is **Option C**: The big holes in Swiss cheese are made by a bacterium that produces a large amount of carbon dioxide.

### Final Answer:
The big holes in Swiss cheese are made by a bacterium which produces a large amount of carbon dioxide, specifically **Propionibacterium shermani**.

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