When approaching an intersection controlled by a Stop sign, the correct action is to stop completely and yield to all other vehicles. This requirement is essential for ensuring safety at intersections where visibility may be limited and where there's potential for conflicting traffic flows. A complete stop allows drivers to assess the situation thoroughly and make informed decisions about when it is safe to proceed. Yielding to all vehicles means that if other cars are coming from either direction, they must be allowed to go first. This not only helps prevent collisions but also reinforces the importance of being cautious and aware of the surroundings when navigating intersections. The other options suggest varying degrees of stopping or yielding that do not comply with the legal requirements for a Stop sign. They either imply that it is acceptable to proceed without a complete stop or to only yield to certain vehicles, which could lead to dangerous situations on the road.