The answer is A) the slope of the line is 0
The slope of a line is equal to the change in y values between two points, divided by the change in x values between two points. Or, [tex]\frac{y_{2} - y_{1}}{x_{2} - x_{1}}[/tex].
For a horizontal straight line, the slope is always equal to 0. This is because between any two points on the line, the y-value does not change but the x-value changes. Since we divide the change in y by the change in x, the slope of such a line is 0 divided by another number. 0 divided by anything equals to 0.
Alternatively, for a vertical line the slope is always undefined. This is because to find the slope of such a line, something is divided by 0. And something divided by 0 is always undefined.
