Chalk and programmable logic controller: what they have in common

1. Step 1. Chalk — is a kind of — Lime. Chalk is calcium carbonate, like limestone.
2. Step 2. Lime — uses — Kiln. Lime is made by burning limestone.
3. Step 3. Kiln — is used in — Brick. Fired brick is stronger than mud brick.
4. Step 4. Brick — is material for — Chemical plant. The furnaces and towers are brick.
5. Step 5. Chemical plant — has part — Programmable logic controller. Process control automation.

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