While cooking, if the bottom of the vessel is getting blackened on the outside, it means that

Options

A. the food is not cooked completely.
B. the fuel is not burning completely.
C. the fuel is wet.
D. the fuel is burning completely.

Explanation

### Step-by-Step Solution:

1. **Observation**: While cooking, you notice that the bottom of the vessel is getting blackened on the outside.

2. **Understanding the Cause**: The blackening indicates that something is wrong with the combustion process of the fuel being used for cooking.

3. **Combustion Process**: Normally, combustion is a chemical reaction where a fuel reacts with oxygen to produce carbon dioxide (CO₂) and water (H₂O). This is known as complete combustion.

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