A function can return a unique value (y) for an input value x.
The ordered pairs are in the form (x,y)
In the last set, we can see that
(2,-2) and (2,7)
The input value 2 gives 2 different output values (-2 and 7)
Therefore, that set doesn't represent a function.
Correct option: {(2, 2), (0, -8), (2,7), (-3,8)}