What is peculiar about Swiss cheese ?

Explanation

### Step-by-Step Solution:

1. **Understanding Cheese Formation**:
- Cheese is produced through a process called fermentation, which occurs in the absence of oxygen. This process can involve various microorganisms such as bacteria, fungi, or yeast.

**Hint**: Remember that fermentation is a key process in cheese making and involves microorganisms.

2. **Lactic Acid Fermentation**:
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