What is the primary reason for having a dual air brake system?

Answer: B — Less chance of total brake failure

The primary reason for having a dual air brake system is to reduce the likelihood of total brake failure. In a dual air brake system, there are two separate air brake circuits. This means that if one circuit fails due to a leak or any other issue, the other circuit can still function and provide adequate brake power. This redundancy is crucial for safety, especially for larger vehicles that might require more robust braking systems. Having this dual setup means that operators can rely on a backup in case of failure, which significantly enhances the overall safety of the vehicle. The dual air system is designed to ensure that even in the event of a malfunction, stopping distances remain manageable, and the driver can maintain control over the vehicle. The other options, while they may sound beneficial, do not address the critical safety feature provided by a dual air brake system.