Final answer:
On-duty time includes inspecting or servicing a vehicle, waiting due to unanticipated events, and traveling as one of two drivers not in the sleeper berth. Hence, the answer is all of the above.
Step-by-step explanation:
On-duty time for drivers include a variety of activities not limited to driving time. Specifically, on-duty time includes the time spent inspecting or servicing a vehicle, as well as waiting along the route due to an unanticipated event. Moreover, it encompasses the time traveling as one of two drivers when not resting in the sleeper berth. Therefore, the correct answer is d. All of the above. This comprehensive understanding of on-duty time ensures compliance with relevant labor and duty regulations, and it is fundamental for proper scheduling and adherence to safety standards.