Which of the following is a requirement for a vehicle to be classified as a moped?

To classify a vehicle as a moped, it is essential that the engine piston displacement is 50 cubic centimeters or less. This specific criterion is a defining characteristic that differentiates mopeds from other types of motorcycles or motor vehicles. It helps regulate and categorize vehicles for safety and licensing purposes.

While other factors such as maximum speed, the number of wheels, and seating capacity are relevant to the classification of two-wheeled vehicles, they are not universal requirements for all mopeds. In certain jurisdictions, the maximum speed and design may vary, but the engine displacement remains a consistent factor across regulations that define what constitutes a moped.