7. GradPoint
Which relation is a function?


A. {(1, 4), (1, 3), (1, 2), (1, 1)}

B. {(3, 4), (3, 3), (1, 2), (1, 5)}

C. {(3, 4), (2, 4), (5, 1), (3, 5)}

D. {(1, 3), (2, 6), (3, 9), (4, 12)}