A continuous supply of water is required for which type of attack line?

A continuous supply of water is essential for both the backup line and the regular line because these types of attack lines are commonly deployed in situations that require sustained firefighting efforts. The regular line is typically used for initial attack, providing the necessary water supply to extinguish the fire effectively.

The backup line, on the other hand, is often utilized to support the operation of the regular line, ensuring that additional water is available in case of changes in the fire's intensity or when personnel need to advance further into the fire zone. Both lines are critical in maintaining water pressure and flow, which is crucial for effective fire suppression.

In contrast, the tank line operates independently of a continuous water supply, as it relies on water carried within the tank on the apparatus. Consequently, it is not suitable for prolonged firefighting but can be used for initial attacks or in situations where immediate water is needed without the capability of connecting to a hydrant or continuous source. Therefore, the correct answer identifies that both the backup line and the regular line require a continuous water supply to function effectively in a firefighting scenario.