Answer:
B
Explanation:
I believe it is B because it is the only one that doesnt have x values that repeat and give different answers.
Ex. For a, the x value in the first and third coords gives both 1 and 3 as answers.
Every x has to have a unique y value, so
(2,10) (3,12) is ok, but (2,10) (2,12) is not.
Sorry if this doesnt make sense haha