Which two systems are commonly used for the extension of aerial devices?

The correct choice identifies cable and hydraulic systems as the common means for extending aerial devices. Cable systems utilize a series of cables and pulleys to facilitate the extension and retraction of the aerial ladder or platform. This system is favored for its ability to provide precise control and significant strength, ensuring the stability and safety of the aerial device during operation.

Hydraulic systems, on the other hand, make use of hydraulic fluid to power the movement of the aerial device. These systems are known for their ability to lift heavy loads and provide smooth, controlled movement. Hydraulic operation allows for quick deployment and retraction, which is essential in emergency situations.

The combination of cable and hydraulic mechanisms provides a reliable and efficient means of extending aerial devices, making them a standard choice in firefighting and rescue operations. Other options may suggest systems that can be used in different applications, but they do not encompass the primary and most effective systems utilized for aerial extensions within fire apparatuses.