The graph of a function is shown:



which of the following correctly identifies the set of outputs?

a: {(5,-2), (1,-1), (-2,2), (2,5)}

b: {(-2,5), (-1,1), (2,-2), (5,2)}

c: {-2, -1, 2, 5}

d: {-2, 1, 2, 5}