Which of the following ordered pairs represents a function?

A. {(1, 2), (2, 3), (3, 4), (4, 5)}
B. {(1,5),( 2, 6), (2,7), (1, 6)}
c. {(-2, 2), (3, 2), (-5, 2), (-2,-2)}
D. {(-3,0), (-3, 1), (-3, 2), (-3,3)}​