Hint:The image formed by the concave mirror is bigger than the object; it will be upright and virtual. The image will be behind the mirror. The mirror used in an automobile should gather a large area of the rear field into the small image for safety purposes. Using the function of the three types of mirrors and the purpose of the rear view mirror, we can find the correct answer.
In a convex mirror, the mirror coating is inside the spherical surface. The image formed by the convex mirror is smaller than the object; it will be upright and virtual. The image will be closer to the mirror as compared to the object whereas, in the concave mirror, the mirror coating is outside the spherical surface.
The image of the rear field of view should be virtual, focused and very small in size and the mirror could form a clear distinct image when the other vehicles are very far. This type of image is produced by using a convex mirror.
Thus, it is most suitable to use a convex mirror as the rear view mirror. Other places where a convex mirror is used are hospital apartments, metros, traffic mirrors. The concave mirrors are used in telescopes, medical instruments, shaving mirrors etc. because it produces a magnified image of the object.
Hence, option B is the correct answer.
Note:We need a mirror in an automobile to see the maximum area of the rear field and it should be able to produce a very small image of the rear field for safety while turning and the driver must have an idea about the other vehicles around him. Convex mirror covers a large field of view and forms a small image of the traffic behind the car.