What must you do while entering a roundabout?

Answer: B — Yield to the right

While entering a roundabout, you must yield to the right. This means that you must allow any vehicle already in the roundabout to pass before you enter. Options A, C, and D are incorrect as they do not accurately reflect the specific action of yielding to the right. Proceeding cautiously, significantly reducing your speed, or stopping and waiting your turn may not necessarily allow other vehicles to pass before you enter the roundabout. It is also important to note that roundabouts are designed for continuous traffic flow, so stopping or significantly reducing your speed can disrupt the flow of traffic and potentially cause a collision.