Which of the relations given by the following sets of ordered pairs is a function?

A. ((-2,5), (7, 5), (4, 0), (3, 1), (0,6))

B. ((1,2), (2, 3), (3,4), (2, 1), (1, 0))

C. ((2-8), (6, 4), (-3, 9), (2, 0), (5, 3))

D. ((1,3), (1, 1), (1, 1), (1,3), (1,5)}