Choose the incorrect statement from the following.
A good fuel is one which:

Options

A. is readily available.
B. produces a large amount of heat.
C. leaves behind many undesirable substances.
D. burns easily in air at a moderate rate

Answer

To solve the question, we need to analyze the statements given about what constitutes a good fuel. Let's break it down step by step:

### Step-by-Step Solution:

1. **Understanding the Definition of Good Fuel**:
A good fuel is typically characterized by certain properties that make it efficient and safe for use.

2. **Evaluating the Options**:
We need to evaluate each statement provided in the question to determine which one is incorrect.

3. **Statement Analysis**:
- **Statement 1**: "A good fuel is readily available."
- This statement is true. A good fuel should be easily accessible to ensure consistent usage.

- **Statement 2**: "A good fuel produces a large amount of heat."
- This statement is also true. A good fuel should generate sufficient heat to be effective for its intended purpose (e.g., cooking, heating).

- **Statement 3**: "A good fuel leaves behind many undesirable substances."
- This statement is incorrect. A good fuel should ideally leave behind minimal undesirable substances (like soot, ash, or harmful gases) to be considered efficient and environmentally friendly.

- **Statement 4**: "A good fuel burns easily in air at a moderate rate."
- This statement is true. A good fuel should ignite easily and burn steadily to provide a consistent energy output.

4. **Conclusion**:
Based on the analysis, the incorrect statement is **Statement 3**: "A good fuel leaves behind many undesirable substances."

### Final Answer:
The incorrect statement is: **"A good fuel leaves behind many undesirable substances."**

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