Which of the following sets of ordered pairs is not a function?

{(0, 2), (1, 4), (2, 5), (3, 6)}
{(-1, 2), (1, 3), (1, 5), (-3, 4)}
{(0, 2), (1, 2), (2, 2), (3, 2)}
{(-4, 3), (-1, 1), (-2, 5), (3, 7)}

The answer is {(-1, 2), (1, 3), (1, 5), (-3, 4)} becuase in the x-cordnet there is two one and the rule is "for ever x-aixs theres a y-aixs" but there is two of the same xs so therefore the second answer is not a function.

The answer would be option 4