Which statement best describes the back-up line's role?

Which statement best describes the back-up line's role?

• A. It is used to drain water away from the fire scene.
• B. It is used to replace a failed primary line on the same nozzle.
• C. It is used only as a standby line that is never deployed.
• D. It is intended to relieve the primary line or provide water to a second point of attack.

Answer: (D)