Which of the following is a common sign of air leaks in the air brake system?

Answer: B — Hissing sounds

A common sign of air leaks in the air brake system is the presence of hissing sounds. These sounds often indicate that pressurized air is escaping from the system, which can occur at various points, such as from a damaged hose or fitting. When air escapes, it not only creates audible noise but also compromises the braking efficiency and can lead to system failures if not addressed. Hissing sounds alert the driver or technician to inspect the air brakes for potential leaks to ensure the vehicle operates safely and effectively.