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

A vertical mirror is placed, so the object on the left will appear right in reverse position and vice-versa.

So the triangle at right side (with vertical lines) will be reversed and now will appear at left side, thus the first and third options will be eliminated.

Also, in the question figure, the black triangle at the top will still stay at the top pointing downwards, hence fourth option is the right image.

=> Ans - (D)