In which set of ordered pairs is y a function of x?

A. {(–1, 2), (0, 1), (0, 2), (1, 1)}

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

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

D. {(2, 5), (3, 6), (6, 5), (2, 7)}