Final answer:
The size of the image of the man remains the same as the distance between the man and the mirror increases.
Step-by-step explanation:
As the distance between a man and a plane mirror increases, the size of the image of the man produced by the mirror remains the same. A plane mirror forms a virtual image that is upright and the same size as the object. The distance between the mirror and the image is equal to the distance between the mirror and the object.