Concept:A ray passing through the centre of curvature is incident normally on the mirror.Explanation:The centre of curvature of a concave mirror lies on its principal axis at distance equal to the radius of curvature.Any ray directed through the centre of curvature meets the mirror along the normal to the surface.Therefore, the angle of incidence is 0∘.By the law of reflection, the angle of reflection is also 0∘.So the ray is reflected back along the same path.Answer:The ray is reflected at 0∘.Correct option: C. 0∘.