Final answer:
When approaching a roundabout, vehicles must yield to traffic in the roundabout. This safety rule helps maintain a smooth flow and prevent accidents. The correct answer is option (D) Yield to traffic in the roundabout.
Step-by-step explanation:
Vehicles approaching a roundabout have specific rules to ensure the safe and efficient flow of traffic. One primary rule is that vehicles must yield to traffic in the roundabout. Yielding is crucial because it prevents collisions and allows for the continuous movement of vehicles already navigating the roundabout.
Approaching vehicles should slow down and be prepared to stop if necessary to allow traffic within the roundabout to pass. They should not enter the roundabout at a fixed speed like 35 mph because the appropriate speed can vary depending on conditions, such as weather, traffic volume, and the size of the roundabout itself. Moreover, entering to the left of the central island is incorrect since in many places, roundabouts require entering to the right. Lastly, bringing a vehicle to a complete stop is not always required unless the traffic in the roundabout is too dense to merge safely.
Therefore, the correct option for what vehicles must do when approaching a roundabout is (D) Yield to traffic in the roundabout.