Answer:
To determine if they are functions or not, each y value needs to have only one x value. There should never be 2 values with the same x.
The first one is a function.
The second one is not a function because there are two coordinates that have -1.
The third on is not a function because there are two of them that have 0.
The fourth one is a function because when listing the inputs and outputs, there are different x values for each y value.
Hope this helps ;)