Answer : 4. "flat, convex"
Explanation :

Flat Mirror (or Plane Mirror): Reflects light without distorting the image. The image formed is erect (upright) and of the same size as the object, but reversed from left to right.

Convex Mirror: Also produces an erect image. The image formed is virtual (cannot be projected onto a screen), smaller than the actual object, and upright.

Both flat and convex mirrors can create upright (erect) images of real objects.