Final answer:
Commercial vehicles such as school buses, public passenger vehicles, and vehicles transporting explosives are all required to carry fire extinguishers for safety reasons.
Step-by-step explanation:
The types of commercial vehicles that are required to carry fire extinguishers include school buses, public passenger vehicles, and vehicles transporting explosives. It is a safety regulation to have fire extinguishers on board in case of a fire emergency. This helps ensure the safety of passengers, the driver, and other road users. Therefore, the correct answer to which types of commercial vehicles are required to carry fire extinguishers is d. All of the above.