Final answer:
A CDL is not required for operating the combination vehicle in question because the GVWR of the towed unit does not exceed the 10,000 pounds threshold, despite the GCWR being over 26,001 pounds.
Step-by-step explanation:
The question is related to a CDL (Commercial Driver's License) requirement for operating a specific combination vehicle. The gross vehicle weight rating (GVWR) of the power unit is 21,001 pounds and the GVWR for the towed unit is 5,000 pounds. The gross combination weight rating (GCWR) is 26,001 pounds. According to the Federal Motor Carrier Safety Administration (FMCSA), a CDL is required for vehicles with a GVWR of 26,001 or more pounds provided the GVWR of the vehicle(s) being towed is in excess of 10,000 pounds. In this case, however, although the GCWR is over 26,001 pounds, the GVWR of the towed unit is only 5,000 pounds, which does not exceed the 10,000 pounds threshold. Therefore, based on the provided weight ratings, a CDL would not be required for operating this specific vehicle combination.