Which set of orderd pair represent a function? explain briefly

Question

{(1,0),(2,1), (2,3)}

{(1,3),(1,4), (1,5)}

{(1,5),(2,2), (3,5)}

{(3,1),(2,2), (3,3)}

{(3,2),(5,1), (4,0)}

Answer 1

the 1st, 2nd and 4th set of points are not functions, because they have more than one y value for a given x value.

that leaves the 3rd and 5th. both are functions, but best answer is 5th

as the 3rd is not a one to one function. It has more than one x value for a given y value

go with the last set