Which scenario indicates that your single brake system may need maintenance?

Answer: C — Compressor runs continuously at 90 psi

The scenario where the compressor runs continuously at 90 psi indicates that your single brake system may need maintenance because it suggests that the air system is not maintaining proper pressure. In a well-functioning brake system, the compressor should cycle on and off, creating and maintaining the appropriate pressure for the brakes to function effectively. If the compressor is running continuously, this could mean that it is struggling to build pressure or that there is a leak in the air system, which prevents the pressure from stabilizing. The other scenarios, while they may also indicate issues, are less directly related to the compressor's operation. A burning smell typically points to overheating brakes, while unexpected drops in brake pressure and a sinking brake pedal may reflect different functional or fluid-related problems, but they do not provide the same insight into the operational state of the compressor and air system.