The table on the far right represents a function. This is because a function must have no duplicate x-values. Every input value (x) has to correspond with an individual output value (y). The three tables on the left all have duplicate x-values.
It doesn't look like any of these represent a function. If you look at the input (X), there are repeating numbers in all of them. You cannot have a function if the input numbers are repeating.
