When the object is kept at point C, in the case of a concave mirror, what is the size of the image?

When an object is placed at the centre of curvature (C) of a concave mirror, the image formed is real, inverted, and of the same size as the object. This is because the centre of curvature is located at a distance equal to twice the focal length of the mirror, which makes the image distance equal to the object distance.