Which set of ordered pairs represents a
function?
A. {(-1, 1), (0,0),(1, 1), (2, 2)}
B. {(3,-3), (2,-2),(1,-1),(1, 1)}
C. ((4,2), (4,-2),(9,3), (9,-3))
D. {(-2,-1), (-2,0),(-2,1),(-2,2)}