Answer:
R
Step-by-step explanation:
A vertical line has slope that is "undefined". Line R is the vertical line on your graph.
_____
The slope of a vertical line is "undefined" because of the way slope is defined. Slope is the vertical change divided by the horizontal change. When the line is vertical, there is no horizontal change, so the computation of slope involves division by zero. The result of division by zero is "undefined."
