Anaerobic bacteria digest animal waste and produce biogas (change-A). The biogas is then burnt as fuel (change-B). The following statements pertain to these changes. Choose the correct one.

Options

A. Process A is a chemical change
B. Process B is a chemical change
C. Both processes A and B are chemical changes
D. None of these processes is a chemical change.

Answer

To solve the question regarding the changes involving anaerobic bacteria digesting animal waste to produce biogas and the subsequent burning of biogas as fuel, we can break it down step by step:

### Step-by-Step Solution:

1. **Identify Change A**:
- Anaerobic bacteria digest animal waste.
- This process produces biogas.
- **Conclusion**: In Change A, animal waste is transformed into biogas through the action of anaerobic bacteria. This is a chemical change because new substances (biogas) are formed.

2. **Identify Change B**:
- The biogas produced is then burnt as fuel.
- When biogas is burned, it produces energy and ash.
- **Conclusion**: In Change B, the burning of biogas results in the formation of new substances (energy and ash). This is also a chemical change.

3. **Analyze the Statements**:
- We need to determine which statement correctly describes the changes A and B.
- Since both changes involve the formation of new substances, they are both examples of chemical changes.

4. **Choose the Correct Statement**:
- The correct statement would highlight that both changes involve chemical changes where new substances are formed.

### Final Answer:
The correct option is that both Change A and Change B involve chemical changes because new substances are formed in both processes.

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