When is it permissible to drive on the shoulder of the road?

Answer: B — Only to stop for an emergency

Driving on the shoulder of the road is permissible only in emergencies, such as when a vehicle has broken down, or you need to stop temporarily for safety reasons. The shoulder is designed to provide a space for vehicles in distress, allowing them to be out of the main traffic lanes and reducing the risk of accidents. The other options involve uses of the shoulder that could endanger both the driver and other road users. For example, using the shoulder to pass another vehicle is illegal and can lead to dangerous situations, as the shoulder does not provide an adequate space for passing, nor is it intended for that purpose. Similarly, avoiding heavy traffic by driving on the shoulder is not allowed because it disrupts the flow of traffic and can lead to confusion and accidents. Parking on the shoulder is also not permitted unless it's an emergency, as it can obstruct other vehicles and create hazards on the road. Hence, the designated purpose of the shoulder reinforces the idea that it should only be used for emergency stops.