Which of the following sets of ordered pairs (x, y) represent y as a function of x? *
O {(4,-2), (1,-1), (0,0), (4,2)}
O {(1,2), (1,3), (1,4), (1,5)}
O {(-1,1),(0,0), (1,1), (2, 2)}
O {(2.5,8), (3.5,8), (2.5, 2), (4.5, 2)}