What happens if too much air pressure is built up in the air brake system?

Answer: B — The safety valve will open

When too much air pressure builds up in the air brake system, the safety valve opens to release the excess pressure. This is a crucial safety feature designed to prevent damage to the braking system and potential brake failure. The safety valve helps maintain the pressure within a safe operating range by venting off any surplus air, thereby ensuring the system continues to operate effectively under normal conditions. This feature is particularly important because excessive pressure can lead to mechanical failures and potentially hazardous situations for both the driver and others on the road. While other potential consequences of air pressure issues exist, the primary and immediate action taken to mitigate excess pressure is the opening of the safety valve.