Which of the following statements best describes the effect of replacing the graph of y = f(x) with the graph of y = f(x) + 20?
The graph of y = f(x) will shift left 20 units.
The graph of y = f(x) will shift down 20 units.
The graph of y = f(x) will shift up 20 units.
The graph of y = f(x) will shift right 20 units.