Under what circumstance can you drive on a sidewalk?

Answer: B — When entering or exiting a driveway or alley

Driving on a sidewalk is primarily restricted as it poses risks to pedestrians and can cause accidents. The correct situation where it is permissible is when entering or exiting a driveway or alley. This is because, in this context, it is necessary for vehicles to cross a short section of the sidewalk in order to access the road from private property, such as a driveway. Drivers are expected to yield to pedestrians in this scenario, minimizing any potential danger. The intent of allowing this practice is to facilitate safe transitions between private properties and public streets without disrupting pedestrian traffic more than necessary. Other scenarios like navigating around a traffic jam, parking, or responding to emergency situations do not justify driving on sidewalks and could lead to unsafe situations for pedestrians.