………………. Is used for burning fuel in the rockets and space ships.

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks for a substance that is used to burn fuel in rockets and spaceships.

2. **Identifying the Key Concept**: In the context of rockets and spaceships, combustion is a critical process that requires a supporter of combustion.

3. **Recognizing the Supporter of Combustion**: Oxygen is known to be a supporter of combustion. It does not burn itself but is essential for burning other fuels.

4. **Specific Form of Oxygen**: In the aerospace industry, liquid oxygen is commonly used because it is highly efficient and can be stored in a compact form.

5. **Conclusion**: Therefore, the answer to the question is "Liquid Oxygen."

**Final Answer**: Liquid Oxygen is used for burning fuel in the rockets and spaceships.

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