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). So, the right diagonal in the question figure will appear as left diagonal, thus the last two options are eliminated.

Also, the curve at one end of the line is facing the base, in the mirror it will face the opposite side of base, i.e. top, and thus first option is invalid.

=> Ans - (B)