What tool can be used to check air pressure in the brake system?

Answer: B — pressure gauge

The correct answer is a pressure gauge, which is specifically designed to measure the air pressure in a brake system. This tool is essential for ensuring that the air brake system is functioning properly, as it allows you to monitor the pressure levels within the system. Proper air pressure is crucial for effective braking performance; if the pressure is too low, the brakes may not engage effectively, which could lead to unsafe driving conditions. A torque wrench, while useful for measuring the amount of torque applied to bolts and nuts (important for various mechanical tasks), is not designed to measure air pressure. A brake lining thickness gauge is used to measure the wear of the brake lining material, helping to determine when it needs replacement, but it does not provide any information regarding air pressure. A multimeter is primarily used for measuring electrical properties such as voltage, current, and resistance, and is not applicable in measuring air pressure within a braking system. Therefore, the pressure gauge is the appropriate tool for this specific task.