2. In which choice is y a function of x?

A. (1, 3), (3, 4), (4, 5), (5, 6)
B. (2, 0), (2, 3), (4, 5), (6, 7)
C. (2, 5), (4, 8), (6, 10), (2, 12)
D. (6, 2), (4, 1), (6, 8), (8, 10)