Which pair of points lie on a line with an undefined slope?

Question

a. (0,4) (4,0)
b. (0,2) (2,2)
c. (4,0) (4,4)
d. (4,4) (2,2)

Answer 1

c. has infinite slope. The slope is (y2 -y1)/(x2 - x1) and the denominator is zero.