Answer: (a) is less than one.
Convex mirrors are used in vehicles for rearview due to the wide or broad field of vision or view, which helps an individual see the number of cars coming from behind.
The convex mirror forms an erect, virtual, and minified or diminished representation or image of the object. Hence, the magnification denoted by (m), brought forth by a rearview reflector or mirror fitted in automobiles or vehicles, is less than 1.
On the other hand, if the magnification is more than or equal to 1, then the height of the image will be greater or equal to the size or height of the object, which would lead only to viewing the only part of the image and hence, it will not provide the detailed idea of the movement of vehicles following the vehicle of an individual.