Crutch uprights and turbine: what they have in common

1. Step 1. Crutch uprights — is part of — Crutches. Two uprights.
2. Step 2. Crutches — evolved into — Wheelchair. Mobility aids.
3. Step 3. Wheelchair — has part — Wheel. Wheels.
4. Step 4. Wheel — includes — Water wheel. A water wheel is a wheel with paddles turned by flowing water.
5. Step 5. Water wheel — evolved into — Turbine. The water turbine evolved from the water wheel.

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