If a mirror is placed on the line MN, then which of the answer figures is the right image of the given figure?

A horizontal mirror is placed, so the objects will turn upside down in the mirror image (e.g - an object at top right will appear at bottom right). Now, the three circles form a right diagonal in the question figure, hence they will appear as left diagonal in the mirror image, thus the third option is eliminated.

Also, the circle at the top right has horizontal diameter, now in the mirror it will appear at bottom right position as shown in last figure.

=> Ans - (D)