Is the line for the equation y = - 8 horizontal or vertical? what is the slope of this line? select the best answer. a) the line is horizontal. the slope is undefined. b) the line is horizontal. the slope is 0. c) the line is vertical. the slope is undefined. d) the line is vertical. the slope is 0.

B) The line is horizontal. The slope is 0

To answer the question above, take note that the equation of the line may be expressed in slope - intercept form,
                                 y = mx + b
where m and b are slope and y-intercept, respectively. 
From the given above, there is no term involving the variable x signifying that the slope is zero. The answer therefore is letter B. The line is horizontal. The slope is 0.