How are fungi useful to us?

Explanation

### Step-by-Step Solution:

1. **Source of Food**: Fungi are an important source of food for humans. An example of this is mushrooms, which are widely consumed and appreciated for their flavor and nutritional value.

2. **Baking and Fermentation**: Yeast, a type of fungus, is crucial in the baking industry. It helps in the fermentation process, which is essential for making bread rise. Additionally, yeast is used in the production of alcoholic beverages such as wine and beer.

3. **Nutritional Value**: Some fungi, like certain types of yeast, are rich in vitamin B12, which is important for maintaining healthy nerve cells and producing DNA.

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