What must be activated immediately upon parking on a roadway if a vehicle is larger than specified?

Answer: B — Hazard lights

When parking a larger vehicle on a roadway, it is essential to activate the hazard lights immediately. Hazard lights serve as a critical warning to other drivers, indicating that your vehicle is stationary and may present a potential hazard in the flow of traffic. This is particularly important for larger vehicles, which can obstruct visibility and traffic movement, especially when parked on or near busy roads. Activating the hazard lights helps ensure that other road users are aware of your vehicle's presence, reducing the risk of accidents. Using emergency lights is important, but in the context of a stationary vehicle on the roadway, hazard lights specifically focus on alerting others to the situation. Tail lights are typically used to indicate the vehicle is operational or braking, and a left turn signal is primarily for indicating upcoming turns, neither of which provide the necessary warning in this scenario. Therefore, activating hazard lights is a critical step for safety when parking larger vehicles on the roadway.