ASSERTION: For observing traffic at our back we prefer to use a convex mirror
REASON: A convex mirror has a much larger field of view than a plane mirror or a concave mirror
A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
B. Both Assertion and Reason are correct and Reason is not the correct explanation for Assertion
C. Assertion is correct but the Reason is incorrect
D. Both Assertion and Reason are incorrect

Hint: We have to observe both the assertion and reason statements keeping in mind the nature of both concave and convex mirrors which gives us the nature, structure and shape, position of the focus, and image projection. Among the two we have to select the one which provides virtual, erect, and diminished images irrespective of the distance of the object. This is to view a larger amount of area behind the vehicle.

Complete answer:
The convex mirror forms virtual, erect, and also diminished images irrespective of the distance of the object. A convex mirror helps a driver to view a large part of the area of traffic behind him. The convex mirror forms a very smaller image than the object and occupies less space. We prefer a convex mirror over a concave as a rear-view mirror in vehicles because it gives us a wider field of view, which helps the driver to see most of the traffic behind him.
The image shown by a convex mirror is always virtual and located behind the mirror. When the object is far away from the mirror, the image is upright and is located at the focal point. As the object comes nearer to the mirror, the image also comes nearer to the mirror and grows until its height is equal to that of the object. The image that is formed by convex mirrors is smaller than the object but it gets bigger as they approach the mirror. But The Concave mirrors reflect parallel rays of light closer together to form a real image at the focus. Hence option A) Both Assertion and Reason are correct and the reason is the correct explanation for Assertion.

Note: A convex mirror always forms a small and upright image between pole and focus which helps the driver to see all the traffic coming behind in a small area of the mirror. It is also used as a reflector in street lamps and also as a vigilance mirror. When two convex mirrors are placed one behind the other we can also make a magnifying glass.