Final answer:
The correct action when driving a commercial vehicle over 13 feet tall is to stop and make sure if a clearance is high enough. Assumptions should not be made about clearances, even on state or federal highways.
Step-by-step explanation:
When driving a commercial vehicle with a height over 13 feet, the correct course of action is: a. If you aren't sure a clearance is high enough, stop and make sure. It's essential for the safety of everyone on the road and the integrity of the vehicle and infrastructure that drivers of tall vehicles confirm that the clearance is sufficient for their vehicle to pass through safely. Not doing so can lead to accidents, traffic disruptions, and potential legal issues for ignoring clearance heights and road regulations.
Options b and c are incorrect because they can lead to dangerous assumptions potentially causing accidents and property damage. It is crucial to know that while most state and federal highways are designed to accommodate commercial vehicles, exceptions exist, and caution should always be exercised regarding vehicle clearances.