Final answer:
Supervising drivers must have held a Class C license for at least 2 years.
Step-by-step explanation:
The supervising drivers must have held at least a Class C license for 2 years. This means that they must have possessed a Class C license for a minimum of 2 years before they can supervise another driver. This requirement is in place to ensure that supervising drivers have the necessary experience and knowledge to effectively guide and mentor new drivers.