Where must the water supply for attack lines and backup lines come from?

The correct answer emphasizes the importance of redundancy and reliability in fire operations. When firefighting, especially in scenarios involving attack lines and backup lines, a single water source can be risky. If that source becomes compromised due to a failure or blockage, both lines would be rendered ineffective. By utilizing two separate sources, firefighters ensure that even if one line encounters problems, the other remains operational, thereby maintaining adequate water supply for effective fire suppression.

In addition, strategic planning around water supplies allows for a more flexible approach in different firefighting situations. This redundancy also accounts for the varying demands on water pressure and flow rates that can fluctuate during operations.

The other options do not provide the same level of assurance needed for effective firefighting. A single source, like a hydrant or a nearby pond, could be insufficient or unreliable under certain conditions, making it far less preferable compared to utilizing two separate sources for water supply.