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