What is a regulated heavy vehicle?

• A. All heavy vehicles over 4.5 tonnes.
• B. All heavy vehicles with Federal Interstate registration.
• C. All heavy vehicles with a GVM over 12 tonnes or truck and trailer combinations with a GVM over 12 tonnes or a bus that seats more than 12 adults.
  Explanation:

  "A regulated vehicle is a heavy truck with a Gross Vehicle Mass (GVM) of over 12 tonnes or a truck and trailer combination, if the combined GVM is over 12 tonnes, or a bus that seats more than 12 adults (including the driver). The regulation sets the maximum hours of work and minimum rest periods for drivers of 'regulated heavy vehicles'."