What must you do when approaching a stopped emergency vehicle?

Answer: C — Slow down and, if safe, move over a lane

When encountering a stopped emergency vehicle, it is essential to prioritize safety for both yourself and the responders on the scene. Slowing down and, if it's safe, moving over to a different lane helps to create a buffer zone. This practice not only enhances your visibility but also protects emergency personnel who may be working close to the road. Moving over provides them with the necessary space to perform their duties without the risk posed by passing vehicles, which is crucial for their safety and the safety of anyone involved in the emergency situation. Such measures are often mandated by law in many states, recognizing the hazards that responders face while working on the road.