Chalk and telephone: what they have in common

1. Step 1. Chalk — is material for — Tablet (medicine). Tablet fillers are chalk and starch.
2. Step 2. Tablet (medicine) — is used in — Aspirin. Produced as tablets.
3. Step 3. Aspirin — is made of — Coal. The raw materials of early pharmaceutical synthesis were products of coal tar distillation.
4. Step 4. Coal — is a kind of — Carbon. Mostly carbon.
5. Step 5. Carbon — is material for — Hearing aid. The first hearing aids used a carbon microphone.
6. Step 6. Hearing aid — evolved from — Telephone. The first electric hearing aids were built from telephone components.

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