Final answer:
Improper load securement is one of the main causes of vehicle rollovers, as it can shift the vehicle's center of gravity and increase the risk, especially during sudden maneuvers or on ramps, curves, and turns.
Step-by-step explanation:
One of the main causes of vehicle rollovers is C. Improper load securement. When a vehicle's load is not properly secured, it can shift during transit, especially on ramps, curves, and turns. This shifting can alter the center of gravity of the vehicle, increasing the risk of a rollover, particularly if the vehicle is moving at a high speed or making sudden maneuvers. Additionally, other factors such as driver error, road conditions, and vehicle design can also contribute to the incidence of rollovers.