Which statement describes the rate of change of the following function?
f(x) = 3x + 8
A.
The function has a constant rate of change, increasing for all x at a rate of 8.
B.
The function has a varying rate of change when x > 8.
C.
The function has a constant rate of change, increasing for all x at a rate of 3.
D.
The function has a varying rate of change when x > 3.