What do pneumatic systems primarily use to function?

Pneumatic systems primarily use compressed air to function, which is why this answer is correct. The core principle behind pneumatic systems is the use of compressed air to transmit and control energy. These systems harness air that is compressed in a cylinder or a tank, creating pressure that can be harnessed to power actuators, valves, and other components of machinery.

Compressed air is advantageous in many industrial applications due to its availability, safety, and ease of use. It allows for quick and efficient operation, especially in systems that require rapid movements or need to transmit energy over distances without significant losses.

The other options do not align with the primary function of pneumatic systems. While oil is often used in hydraulic systems for their liquid-based movement and electricity serves electrical systems, neither is suitable for the gas-based operation of pneumatic systems. Water may be used in various applications but is not a fundamental element in pneumatic systems, as it would introduce complications such as corrosion and freezing that are not present with air.