Which set of ordered pairs represents y as a function of x?
A {(2, -1),(4,-2), (6,-3), (8,4)}
B {(0,0), (1, 1), (1,0), (2, 1)}
C {(3, 3), (3,4),(4,3), (4,4)}
D {(1,-5), (1,5), (2, -10), (2, -15)}