When firefighting teams advance to cool a flame-impinged tank, the back-up line should be:

• A. A large-diameter line greater than three inches.
• B. Placed at the ends of the tank for safety.
• C. Established by unmanned nozzles.
• D. Supplied by a separate pump and water source.

Answer: (D)

Redundancy and reliable supply are essential when cooling a tank that’s still burning. The back-up line needs to be kept fully capable even if the primary line’s supply is disrupted, so it should have its own pump and water source. This independence ensures a steady flow to protect firefighters and continue cooling the tank, even if the first line experiences pressure drop, hose issues, or other problems. The other options don’t guarantee that reliable, independent flow: line size isn’t the decisive factor here; placement at the ends of the tank isn’t a universal safety rule for a back-up line; unmanned nozzles remove the necessary firefighter control; and sharing a source or pump with the primary line risks both lines failing together.