Pager and aerosol can: what they have in common

1. Step 1. Pager — has part — Liquid-crystal display. The message appears on an LCD.
2. Step 2. Liquid-crystal display — has part — LED. LED backlighting.
3. Step 3. LED — is part of — Street light. LEDs.
4. Step 4. Street light — evolved from — Gas lamp. Gas lamps.
5. Step 5. Gas lamp — has part — Valve. A gas supply valve.
6. Step 6. Valve — is part of — Aerosol can. A valve.

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