Which two systems are commonly used to extend the aerial device in fire apparatus?

The correct answer is based on the common practice of utilizing hydraulic systems in fire apparatus, particularly for extending aerial devices. Hydraulic systems are preferred due to their ability to generate significant force and allow for precise control when extending heavy loads, which is crucial in emergency situations where time and reliability are paramount.

The use of cable systems in conjunction with hydraulics is also common. Cables can provide additional support and stability for the aerial device while it's being deployed, complementing the hydraulic action. Thus, the combination of cable and hydraulic systems offers both the power necessary for extension and the stability required during operation, making it a widely accepted method for extending aerial devices in fire apparatus.

Other options, while they may involve mechanical means, do not represent the most effective or reliable methods used in modern fire apparatus for extending aerial devices. This specialization highlights the reliance on hydraulic systems as the primary mechanism in conjunction with additional support structures like cables.