Which of the following sets of ordered pairs defines a function?
A. {(2,3), (2,2), (2,1), (2,0)}
B. {(5,3), (4,2), (3,1), (2,0))
C. {(0, -3), (1,-2), (0, -1),(-1,0))
D. (3,1),(-3,2), (4,3), (4,4)}​