B. So that you will be forced to look behind the car for an approaching bicyclist.
Explanation:
This is the main reason why you should open your door with your right hand, as opposed to your left. Most people are used to opening their door with their left hand, as this is easier. However, the advantage of opening the door with your right hand is that it forces you to twist your body and look behind you. By doing so, you are more likely to notice approaching bicyclists, and thus, it might help you avoid accidents.
