The correct answer is the graph is shifted up by 20 units.
When a number is added to or subtracted from f(x), it translates the graph of f(x) either up or down or we can say it moves the graph of f(x) vertically up or down. Addition of a number moves it vertically up and subtraction moves it vertically down.
In this case 20 is being added to f(x), so this will shift the graph of f(x) 20 units up.
