Answer:
A) Undefined slope
Step-by-step explanation:
The slope of a line is the ratio of the change in y to the change in x between any two points on the line.
[tex]\boxed{\begin{array}{l}\underline{\textsf{Slope formula}}\\\\\large\text{$m=\dfrac{y_2-y_1}{x_2-x_1}$}\\\\\textsf{where:}\\\phantom{w}\bullet\;\;m\; \textsf{is the slope.}\\\phantom{w}\bullet\;\;(x_1,y_1)\;\textsf{and}\;(x_2,y_2)\;\textsf{are two points on the line.}\end{array}}[/tex]
Since any two points on a vertical line have the same x-coordinate, the change in x is zero. Consequently, the slope of a vertical line is undefined because division by zero is undefined.
