Air supplied to a pneumatic system is supplied through the __________ line.

• A. Return
• B. Exhaust
• C. Vent
• D. Supply

Answer: (D)

The line that carries pressurized air from the compressor into the system is the supply line. This line delivers the power to valves, cylinders, and other pneumatic components, providing the pressurized air needed for operation. Exhaust or vent lines are used to release air to the atmosphere when pressure is relieved, and a return line would imply air traveling back toward the source rather than feeding the system. Therefore, the line that supplies air to the system is the supply line.