Fluoride and rock drill: what they have in common

1. Step 1. Fluoride — uses — Chemical reaction. It strengthens enamel.
2. Step 2. Chemical reaction — is used in — Capsule. The shell dissolves in the stomach.
3. Step 3. Capsule — is part of — Pneumatic tube. A container for letters.
4. Step 4. Pneumatic tube — uses — Compressed air. Air pressure.
5. Step 5. Compressed air — is used in — Rock drill. Pneumatics.

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