The table shows sets of ordered pads that form a relation

Does each set of ordered pairs represent a function?

Select Function or Not a Function for each set of ordered pairs

{(2,4),(3,1),(0,5),(-1,3)}
{(2,4),(4,1),(0,4), (3,0)}
{(-23),(4,1),(4,4),(3, 2)}
{(7-3),(3; -7), (2,4),(4, 2)}