A) 9
B) 0
C) Undefined
D) 6

Answer:
Step-by-step explanation:
The slope of a horizontal line is equal to 0.
The slope of a vertical line is undefined.
The formula of a slope:
[tex]m=\dfrac{y_2-y_!}{x_2-x_1}[/tex]
Put the coordinates of the pojnts from the graph (2, 9) and (4, 9):
[tex]d=\dfrac{9-9}{4-2}=\dfrac{0}{2}=0[/tex]