What should a driver do when they see a stop sign?

Answer: B — Stop completely, then proceed when safe

A driver must come to a complete stop when they see a stop sign, making option B the correct choice. This action is essential for ensuring safety on the roads, as stop signs are placed at intersections to control the flow of traffic. When a driver stops, they allow themselves the opportunity to assess the situation carefully; they can look for pedestrians, check for oncoming vehicles, and determine if it is safe to proceed. This thorough observation can help prevent accidents and ensure that the driver is obeying traffic laws. In contrast, simply slowing down and proceeding if the way is clear, as proposed in one of the other options, does not fulfill the requirement of a complete stop and could lead to a dangerous situation if another vehicle or pedestrian unexpectedly enters the intersection. Yielding to oncoming traffic without stopping might also lead to confusion and potential collisions, as the stop sign specifically designates that a full stop is required. Ignoring the stop sign altogether is not only unsafe but also illegal, as all drivers are expected to adhere to traffic signs regardless of the presence of other vehicles.