option 4 can be a relation but not a function
For a relation to be a function, there must be two mapping kinds
one to one or many to one
What this mean is that every x value will have a single y-value or many x values to one y value
No single x value will have a two y values
Thus, looking at the options, the circle can be a relation but it is not a function
This is because an x-value will have y-value below and above it