If a mirror is placed on the line MN, then which of the answer figures is the right image of the given figure?
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A vertical mirror is placed, so the object on the left will appear right in reverse position and vice-versa.

So the diagonal originating from top right will now appear from top left, thus the first option will be eliminated.

Also, in the question figure, the square at top right will appear at top left side and the black triangle will stay vertical, hence fourth option is the right image.

=> Ans - (D)