Accordion and internal combustion engine: what they have in common

1. Step 1. Accordion — has part — Bellows. Bellows.
2. Step 2. Bellows — has part — Valve. A valve in the bellows lets air in when they open and keeps it from escaping back.
3. Step 3. Valve — is part of — Internal combustion engine. Valves let in the mixture and let out the gases.

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