12. Which of the following sets of ordered
pairs represents a function?
A. {(0,3), (2, 6), (7, 12), (0, -3))
B. {(6, 1), (6,2), (6,3), (6,4)}
C. {-12,0), (-13, -1), (-14, -2), (-14, -3))
D. {(1, 6), (2, 6), (3, 6), (4, 6)