Which of the following expressions represents a function?
Ax2 y2 = 9
B{(4, 2), (4, –2), (9, 3), (9, –3)}
Cx = 4
D2x y = 5
Ax2 y2 = 9
B{(4, 2), (4, –2), (9, 3), (9, –3)}
Cx = 4
D2x y = 5