Final answer:
Car A has the right of way because it is already stopped at the stop line when Car B is still approaching the intersection, according to the rules for a 4-way stop. The right of way is determined by the order in which the vehicles arrive and come to a complete stop.
Step-by-step explanation:
When two vehicles approach a 4-way stop intersection, the right of way is determined by which vehicle arrives and stops first. If the vehicle on the left, Car A, is already stopped at the stop line while Vehicle B is still approaching 20 feet away from the stop line, then Car A has the right of way because it arrived at the intersection first. However, without specific timing details, this scenario is theoretical, and drivers should always proceed cautiously and confirm the intentions of other drivers before proceeding.
The rule of thumb is that the vehicle that arrives first to a complete stop at the intersection has the right of way. If two vehicles arrive at the same time, the one on the right generally has the right of way. But in the scenario presented, Car A is already stopped, and thus, should be the one to proceed first.