What must you do before entering a roundabout?

Answer: B — Yield to traffic already in the roundabout

Before entering a roundabout, it is crucial to yield to traffic that is already in the roundabout. This rule is important because vehicles inside the roundabout have the right of way, and yielding helps prevent collisions and maintains the flow of traffic. When you approach a roundabout, you should look for signs indicating whether you need to yield and be aware of the traffic conditions within the roundabout. Yielding ensures that you can safely merge into the flow of traffic once there is an appropriate gap, allowing for a smooth transition into the roundabout. This practice promotes safety and efficiency, making roundabouts a safer alternative to traditional intersections.