Weather balloon and oil lamp: what they have in common

1. Step 1. Weather balloon — is made of — Hydrogen. Filled with hydrogen or helium.
2. Step 2. Hydrogen — is used in — Liquid-propellant rocket engine. Hydrogen is an efficient fuel.
3. Step 3. Liquid-propellant rocket engine — is part of — Reusable rocket. Liquid-propellant engines.
4. Step 4. Reusable rocket — is made of — Kerosene. The fuel is kerosene or methane.
5. Step 5. Kerosene — is used in — Kerosene lamp. The fuel.
6. Step 6. Kerosene lamp — evolved from — Oil lamp. A development of the oil lamp.

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