Which of the following items must function properly for a vehicle to pass inspection?

For a vehicle to pass inspection, it is essential that the windshield wipers function properly. Windshield wipers are critical for ensuring that the driver has clear visibility, especially in adverse weather conditions such as rain or snow. A properly functioning set of wipers removes water, dirt, and debris from the windshield, which is vital for safety on the road.

In the context of vehicle safety, items like the air conditioning system, audio system, and navigation system may enhance comfort or convenience for passengers, but they do not directly affect the vehicle's ability to operate safely or its compliance with safety regulations. Thus, they are not mandatory for passing inspection.