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

A horizontal mirror is placed, so the object on the top will appear at the bottom in reverse position and vice-versa.

So the triangle at the top will now appear at the bottom facing towards top, thus the first and last options will be eliminated.

Also, in the question figure, the vertical lines are at top left side of triangle, hence they will appear at bottom left side, hence third option is the right image.

=> Ans - (C)