Answer:
A. 0
Step-by-step explanation:
We must find the slope using the slope formula.
Slope:[tex]m=\frac{y_2-y_1}{x_2-x_1}[/tex]
We substitute [tex]x_1=a\\y_1=b[/tex] and [tex]x_2=c\\y_2=b[/tex]
[tex]m=\frac{b-b}{c-a}=\frac{0}{c-a}=0[/tex]
Slope is 0.
