What do red lights mean?

Answer: B — You must stop and wait behind the white stop line

Red lights indicate that you must stop and wait behind the white stop line. This rule is in place to ensure the safety of all road users, including pedestrians and other vehicles. When the traffic light turns red, it signals that it is not safe to proceed, and stopping ensures compliance with traffic regulations. The other options suggest situations where proceeding or preparing to stop may be appropriate, but they do not apply at a red light. The red light is an absolute signal to come to a complete stop, without any provision for proceeding or turning, which reinforces the need for a clear and safe flow of traffic at intersections.