The two points that lie on a line with an undefined slope are a) (-2,-3) and (2,-6) b) (-2,-3) and (-6, 2 c) (-2,-3) and (2,0) d) (-2,-3 )and (-2,6)

When you know 2 points on a line, the slope of the line is

            (difference in y-values) / (difference in x-values).

The slope of the line that includes the points (-2,3) and (-2,6) ...
choice-d ... is
                         (6 - 3) / (-2 - -2)  =  3 / 0 .

Division by zero is 'undefined'.

(On a graph, these two points are on a vertical line.)