The graphs of functions f(x) and g(x) = f(x) + k are shown:

Graph of line f of x going through ordered pairs 0, negative 2 and 2, 2. Graph of line g of x going through ordered pairs 0, 2 and 1, 4.

What is the value of k?

a
k = −2

b
k = 2

c
k = −4

d
k = 4