What is an important step before entering a roundabout?

Answer: B — Yield to traffic already in the roundabout

Yielding to traffic already in the roundabout is an essential step because roundabouts are designed to enhance traffic flow and improve safety. When you approach a roundabout, the vehicles already circulating have the right of way, meaning that new entrants must wait until it is safe to enter. This practice reduces potential collisions and ensures that traffic moves smoothly through the roundabout. While other options may seem relevant in certain contexts, yielding is the most critical action to take upon arriving at a roundabout to maintain safety and proper traffic flow. For example, turning on headlights may be useful in low visibility situations, increasing speed could lead to dangerous conditions, and signaling left before entering might confuse other drivers since the signal typically indicates that a vehicle intends to exit rather than enter. Therefore, yielding ensures that you respect the rules of the road and the flow of traffic within the roundabout.