Gallium arsenide and plumbing: what they have in common

1. Step 1. Gallium arsenide — is material for — LED. The first LEDs were gallium arsenide phosphide.
2. Step 2. LED — is part of — Street light. LEDs.
3. Step 3. Street light — evolved from — Gas lamp. Gas lamps.
4. Step 4. Gas lamp — has part — Valve. A gas supply valve.
5. Step 5. Valve — is part of — Fire hydrant. A gate valve.
6. Step 6. Fire hydrant — uses — Plumbing. Plumbing.

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