What distinguishes a Dual Air Brake system from other air brake systems?

Answer: C — Two separate air brake systems with a single set of controls

The distinguishing feature of a Dual Air Brake system is that it operates with two separate air brake systems that are controlled by a single set of controls. This design enhances safety, as the redundancy means if one system fails, the other can still operate effectively. This dual setup allows for more reliable braking performance, especially in larger vehicles that require greater stopping force. In contrast, while the use of spring brakes and multiple air tanks may be present in various braking systems, they do not uniquely define a Dual Air Brake system. Additionally, the absence of slack adjusters does not pertain specifically to the characteristic of dual systems but rather relates to the mechanisms of braking efficiency and maintenance.