The formation of soot occurs when

Options

A. there is not enough oxygen for burning and few carbon particles are left unburnt
B. there is enough oxygen for burning carbon particles
C. there is not enough oxygen for burning hydrogen
D. none of these.

Explanation

### Step-by-Step Solution:

1. **Understanding Combustion**:
- Combustion is a chemical reaction that occurs when a substance reacts with oxygen to produce heat and light. It can be complete or incomplete.

2. **Complete vs. Incomplete Combustion**:
- **Complete Combustion**: This occurs when there is a sufficient supply of oxygen, resulting in the complete burning of the fuel. The products are mainly carbon dioxide (CO2) and water (H2O).
- **Incomplete Combustion**: This occurs when there is a limited supply of oxygen. In this case, the fuel does not burn completely, leading to the formation of by-products.

3. **Formation of Soot**:
- When there is not enough oxygen available during combustion, some of the carbon in the fuel does not get oxidized completely. This unburnt carbon appears as black particles, which we refer to as soot.

4. **Conclusion**:
- The formation of soot occurs specifically when there is limited oxygen supply leading to incomplete combustion, resulting in unburnt carbon particles.

5. **Evaluating Options**:
- **Option 1**: "There is not enough oxygen for burning and few carbon particles are left unburned." - This is correct.
- **Option 2**: "There is enough oxygen for burning carbon particles." - This is incorrect because sufficient oxygen would not lead to soot formation.
- **Option 3**: "There is not enough supply of oxygen for burning hydrogen." - This is incorrect as hydrogen does not produce soot.
- **Option 4**: Incorrect for similar reasons as option 3.

### Final Answer:
The correct answer is **Option 1**: "There is not enough oxygen for burning and few carbon particles are left unburned."

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