??? Line L passes through the points (8, 1) and (-9, 1). Which of the
following lines is perpendicular to line L?

A.) y = 2/17X+2
B.) y = -8
C.) X = 5
D.) y= -17/2 X+7

To do this you need the gradient of line L.
Gradient = change in y / change in x
Gradient = 0/17
Gradient = 0
This means that line L is going horizontally on y = 1 and that the other line must be going vertically upwards to be perpendicular.
So the answer is C :)