Flip-flop and aerosol can: what they have in common

1. Step 1. Flip-flop — has part — Vacuum tube. The first flip-flop used vacuum tubes.
2. Step 2. Vacuum tube — uses — Vacuum. Electrons fly in an evacuated bulb.
3. Step 3. Vacuum — is used in — Boyle’s air pump. The pump draws out the air.
4. Step 4. Boyle’s air pump — has part — Valve. Valves.
5. Step 5. Valve — is part of — Aerosol can. A valve.

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