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 flag in the middle (pointing rightwards) will be reversed and will now point to left side, thus the first and last options will be eliminated.

Also, in the question figure, the black circle at top left  will now appear at top right side, hence second option is the right image.

=> Ans - (B)