Which of the following requirements must a driver possessing a CDL fulfill?

A driver possessing a Commercial Driver's License (CDL) must complete both the self-certification process regarding the type of driving they are engaged in and obtain a medical examiner's certificate.

Self-certifying allows the driver to inform the licensing authority of the specific category of driving they will be undertaking, whether it be intrastate or interstate, and whether it involves transporting hazardous materials, operating buses, or other commercial activities. This certification is crucial because it ensures that the driver is compliant with regulations that pertain to their specific driving activities and sets the foundation for further licensing and requirement checks.

Additionally, obtaining a medical examiner's certificate is a regulatory necessity for CDL holders. This certificate ensures that the driver meets the health standards set by the Department of Transportation (DOT), confirming their physical ability to safely operate a commercial vehicle. It is vital to ensure that drivers are physically fit to manage the demands of driving large and potentially hazardous vehicles.

Both these requirements serve to maintain safety on the road by ensuring that commercial drivers are both properly licensed for their specific activities and medically fit to operate their vehicles, making option D the most comprehensive and correct choice.