For an internal combustion engine to move a vehicle down the road,it must convert the energy stored in the fuel into mechanical energy to drive the wheels. In your car,the distributor and battery provide this starting energy by creating an electrical "spark",which helps in combustion of fuels like gasoline. Below is the reaction depicting complete combustion of gasoline in full supply of air:
`2C_8 H_(18)(l) +25 O_(2) (g) to 16 'x' `
‘A student while walking on the road observed that a cloud of black smoke belched out from the exhaust stack of moving trucks on the road.’ Choose the correct reason for the production of black smoke:

Options

A. Limited supply of air leads to incomplete combustion of fuel.
B. Rich supply of air leads to complete combustion of fuel.
C. Rich supply of air leads to a combination reaction
D. Limited supply of air leads to complete combustion of fuel

Answer

To solve the question regarding the production of black smoke from the exhaust of moving trucks, we need to analyze the combustion process of fuel in internal combustion engines.

### Step-by-Step Solution:

1. **Understanding Combustion**:
- Combustion is a chemical reaction where a fuel reacts with oxygen to produce energy, usually in the form of heat and light. In the case of gasoline, the complete combustion reaction can be represented as:
\[ 2C_8H_{18}(l) + 25O_2(g) \rightarrow 16CO_2(g) + 18H_2O(g) \]
- This reaction indicates that when there is a sufficient supply of oxygen (air), gasoline burns completely to produce carbon dioxide (CO2) and water (H2O).

2. **Identifying Incomplete Combustion**:
- Incomplete combustion occurs when there is not enough oxygen available for the fuel to react completely. This can lead to the formation of carbon particles (soot) and other hydrocarbons, which are responsible for black smoke.
- The general reaction for incomplete combustion can be represented as:
\[ C_xH_y + O_2 \rightarrow CO + C + H_2O \]
- Here, carbon (C) is produced as a byproduct, which contributes to black smoke.

3. **Analyzing the Options**:
- **Option A**: Limited supply of air leads to incomplete combustion of fuel. (This is likely the correct answer as it explains the presence of black smoke.)
- **Option B**: Rich supply of air leads to complete combustion of fuel. (This would not produce black smoke.)
- **Option C**: Rich supply of air leads to combination reaction. (This is not relevant to the context of combustion.)
- **Option D**: Limited supply of air leads to complete combustion of fuel. (This is incorrect as limited air would not allow for complete combustion.)

4. **Conclusion**:
- The correct reason for the production of black smoke from the exhaust of moving trucks is **Option A**: Limited supply of air leads to incomplete combustion of fuel.

### Final Answer:
The correct reason for the production of black smoke is: **Limited supply of air leads to incomplete combustion of fuel (Option A).**