Final answer:
A bus driver must have at most seven hours off-duty per day.
Step-by-step explanation:
B. is at most seven hours. According to the information provided, a bus driver must have certain off-duty hours per day. From the options given, 'is at most seven hours' best fits this requirement.
This means that a bus driver can have a maximum of seven hours of off-duty time per day, with the possibility of having fewer hours.
Learn more about Bus driver's off-duty hours