Option (D) is correct because both plane mirrors and convex mirrors always form erect images regardless of the object distance. For a convex mirror, the example in the context shows that the image formed is 'virtual, erect and smaller in size' for an object at 5.00 m distance. The context also mentions that for convex mirrors, we consider two positions - at infinity and at finite distance - and both produce erect images. For a concave mirror, Table 9.1 clearly shows that the image is 'Real and inverted' for most positions (at infinity, beyond C, at C, between C and F). Only when the object is placed 'Between P and F' does a concave mirror form a 'Virtual and erect' image. Therefore, a concave mirror does not always produce an erect image - it depends on the object's position. Hence, the mirror must be either plane or convex.