Big holes in Swiss cheese are made by a

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 Swiss Cheese**: Swiss cheese is known for its characteristic holes or "eyes." These holes are not made by any mechanical process but rather by biological activity.

2. **Identifying the Bacteria**: The specific bacteria responsible for the formation of these holes is called *Propionibacterium shermanii*. This bacterium plays a crucial role in the fermentation process of Swiss cheese.

3. **Role of Lactic Acid**: During the fermentation process, *Propionibacterium shermanii* utilizes lactic acid. This is a byproduct of the initial fermentation of milk by other bacteria.

4. **Gas Production**: As *Propionibacterium shermanii* metabolizes lactic acid, it produces a significant amount of carbon dioxide gas (CO2).

5. **Formation of Holes**: The carbon dioxide gas forms bubbles within the cheese. Over time, these bubbles expand and create the characteristic holes in Swiss cheese.

6. **Conclusion**: Therefore, the big holes in Swiss cheese are primarily due to the action of *Propionibacterium shermanii*, which produces carbon dioxide during its metabolic activity.

### Final Answer:
Big holes in Swiss cheese are made by a bacteria that produces a large amount of carbon dioxide, specifically *Propionibacterium shermanii*.

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