Machine and tank: what they have in common

1. Step 1. Machine — includes — Watt steam engine. A machine.
2. Step 2. Watt steam engine — is part of — Ironclad. Steam engines.
3. Step 3. Ironclad — has part — Armour. An armour belt.
4. Step 4. Armour — is part of — Tank. Armour protects the crew.

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