Fire truck and headphones: what they have in common

1. Step 1. Fire truck — evolved from — Fire pump. A pump on a motor-vehicle chassis.
2. Step 2. Fire pump — is made of — Leather. The hoses were sewn from leather.
3. Step 3. Leather — is material for — Bit and bridle. A bridle is leather straps.
4. Step 4. Bit and bridle — has part — Headband. Straps on the head.
5. Step 5. Headband — is part of — Headphones. A band that presses the cups.

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