Which statement describes the rate of change of the following function?
f(x) = 2x - 8
OA. The function has a varying rate of change when x < 8.
OB. The function has a varying rate of change when x> 2.
OC. The function has a constant rate of change, increasing for all x at a rate of 2.
OD. The function has a constant rate of change, decreasing for all x at a rate of 8.