Final answer:
If the slope of line m is zero, then the slope of line n is undefined.
Step-by-step explanation:
The slope of a line represents the change in the vertical axis divided by the change in the horizontal axis. If the slope of line m is zero, it means that there is no change in the vertical axis for any change in the horizontal axis.
Therefore, the slope of line n, which is perpendicular to line m, is undefined. Perpendicular lines have slopes that are negative reciprocals of each other, so if the slope of line m is zero, line n has an undefined slope.