Question

What are the inputs of the following function?

{(-3, 2), (-4, 2), (8, 3), (7, 1)}

{-4, -3, 7, 8}
{1, 2, 3}
{-4, -3, 1, 2, 3, 7, 8}
{1, 2, 3, 7, 8}