Final answer:
Fast-moving vehicles should use the leftmost lane on highways with three or more lanes going in the same direction to optimize traffic flow and safety. Option a.
Step-by-step explanation:
When there are three or more lanes going in one direction on a highway, fast-moving vehicles should use the leftmost lane. This is to ensure a more organized flow of traffic, where slower-moving vehicles typically use the rightmost lane, and vehicles with a medium pace use the middle lanes. This division allows faster vehicles to pass safely on the left while slower traffic can stay to the right, thus reducing traffic congestion and the chance of accidents.
When there are three or more lanes on a highway, fast-moving vehicles should use the leftmost lane. This is because the leftmost lane is typically designated as the passing lane and is meant for faster vehicles to overtake slower vehicles.