Final answer:
The maximum driving time allowed during a day in Ontario is 13 hours for commercial drivers, as per the Hours of Service regulations.
Step-by-step explanation:
In Ontario, the maximum daily driving time allowed for a commercial driver is governed by the Hours of Service regulations. These rules are in place to ensure that drivers have adequate rest to prevent fatigue-related accidents. According to the regulations, a commercial driver is allowed to drive up to 13 hours within a 24-hour period. This means that the correct answer to the student's question is D. 13 hours.