As per definition of hyperbola difference between the distances of a point on hyperbola from its foci is always constant. This constant distance is equal to the distance between two vertices. Therefore, we can conclude that the difference between the distances of a point on hyperbola from its foci is equal to the length of transversal axis.
Thus, we can conclude that the length of transversal axis of the hyperbola in the given diagram is equal to the difference of the distance m and n.
Hence, length of transversal axis = m-n
Thus, the correct choice is option (c).