After how many hours of being on duty is a driver not eligible to drive under federal regulations?

Answer: B — 60 hours in 7 days

The correct answer highlights the regulatory framework established for commercial drivers regarding hours of service. Federal regulations state that after a driver has been on duty for a total of 60 hours in a 7-day period, they are prohibited from driving until they have completed an off-duty period that resets their driving eligibility. This limit is designed to prevent driver fatigue and ensure safety on the road, as being in control of a commercial vehicle requires high levels of alertness. Drivers must manage their hours effectively to comply with these regulations, as exceeding this limit can lead to penalties and heightened risks of accidents due to impaired judgment caused by fatigue. Understanding these rules is crucial for safety and compliance with federal trucking regulations.