In all mirrors, virtual images are formed when the object is placed at a distance closer than the focal point.
- Plane mirrors always form virtual images that are the same size as the object and appear behind the mirror.
- Concave mirrors can form virtual images if the object is placed closer than the focal point.
- Convex mirrors always form virtual images regardless of the object's position.
Thus, virtual images can be formed by Plane mirrors and Convex mirrors.
Thus, the correct answer is (c).