Bus and chisel: what they have in common

1. Step 1. Bus — is used in — Bus rapid transit. Buses.
2. Step 2. Bus rapid transit — works like — Metro. A metro on the surface.
3. Step 3. Metro — uses — Tunnel. Tunnels.
4. Step 4. Tunnel — uses — Chisel. Hezekiah’s Tunnel was cut by hand with chisels.

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