Rocket stage and gutenberg printing press: what they have in common

1. Step 1. Rocket stage — is part of — Multistage rocket. Each stage is tanks and an engine, dropped once spent.
2. Step 2. Multistage rocket — is a kind of — Rocket. A multistage rocket is a rocket that drops its empty tanks on the way.
3. Step 3. Rocket — is made of — Paper. The first rockets were paper tubes filled with gunpowder.
4. Step 4. Paper — is used in — Gutenberg printing press. The impression is made on paper.

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