which sets of ordered pairs represent functions from a to b select all that ap

Which sets of ordered pairs represent functions from A to B? (Select all that apply.)

A = {a, b, c}
B = {0, 1, 2, 3}

{(a, 1), (b, 2), (c, 3)} {(c, 0), (b, 0), (a, 3)} {(a, 1), (c, 2), (c, 3), (b, 3)} {(1, a), (0, a), (2, c), (3, b)}