Two lines (line a and line b) are parallel to each other. If it cut by a traversal line (line l) then, it form four pairs of corresponding angles and each pair of corresponding angles are same (by Corresponding Angle Axiom)
But, in this question the angle m and angle n are the only a pair of corresponding angle and lines are parallel.
Hence we say that the best represents the relationship between angles m and n is m=n
