The correct option is D ONO
There are two conditions that needs to be satisfied for a word to look the same in a plane mirror,
1). The word must only have letters which will not be affected by lateral inversion
2). The word must be symmetrical about its center letter
"ONO" although satisfies the second condition, but not the first one since "N" is affected by lateral inversion.
Therefore it would not look the same in a plane mirror.