For the function, find the points on the graph at which the tangent line is horizontal. If none exist, state that fact. y=2x+8 List all the points where the tangent line is horizontal. Select the correct choice below and, if necessary, fill in the an A. The point(s) at which the tangent line is horizontal is (are) (Type an ordered pair. Use a comma to separate answers as needed.), B. The tangent line is horizontal at all points of the graph. OC. There are no points where the tangent line is horizontal.