A mirror produces a magnified and erect image of an object. The nature of the mirror is:

In order to answer this topic, we will use the idea of "image production by mirror," in which we essentially study the nature of images produced by various sorts of mirrors.

A plane mirror creates an upright picture that is the exact same size as the item.
Regardless of the object's position, a convex mirror creates a distorted, virtual, and upright picture.
When an item is put between the focus and the mirror pole, a concave mirror creates a magnified, upright, and virtual image (P).

So the correct answer is (C), the nature of the mirror is concave.