Toothpaste and truck: what they have in common

1. Step 1. Toothpaste — is used in — Toothbrush. Toothpaste.
2. Step 2. Toothbrush — is made of — Nylon. Nylon bristles (1938).
3. Step 3. Nylon — is made of — Crude oil. The raw material is petrochemical.
4. Step 4. Crude oil — is used in — Tanker. It carries oil.
5. Step 5. Tanker — has part — Diesel engine. A diesel.
6. Step 6. Diesel engine — is part of — Truck. A diesel engine.

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