When are stop signs present?

Answer: B — When visibility is restricted

Stop signs are present when visibility is restricted, for example at an intersection or where there are obstructions that prevent drivers from seeing oncoming traffic. Option A is incorrect because not every intersection has a stop sign. Option C is incorrect because stop signs may be present at quiet intersections where visibility is poor. Option D is incorrect because not all pedestrian crossings have stop signs, only those where visibility is restricted or there is high pedestrian traffic.