Which of the following relationships represents a function?

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