Which set of ordered pairs in the form of (x,y) does not represent a function of x?
a. {(-1, 2), (3, -2), (0, 1), (5, 2)}
b. {(-1, 2), (3, 2), (-2, 2) (0, 2)}
c. {(-1, 2), (3, -2), (0, 1), (3, 5)}
d. {(-1, 2), (2, 3), (3, -2), (-2, 0)}