Which set of ordered pairs does not represent a function?

{ (-9,0), (-8,8), (-1,-8), (2,8) }

{ (-6, - 2), (-7,-7), (-5,-2), (-9,-8) }

{ (9,6), (-3,-9), (-8, - 1), (9,5) }

{ (-1,-8), (4,1), (-7,-3), (-3,5) }

There is a rule for functions:

One input (x-value) can only have one output (y-value).

If one input has more than one output, it is not a function.

(This doesn't apply to outputs, one output can have more than one input and still be a function)

{ (-9,0), (-8,8), (-1,-8), (2,8) }

This is a function because each input has only one output.

{ (-6, - 2), (-7,-7), (-5,-2), (-9,-8) }

This is a function because each input has only one output.

{ (9,6), (-3,-9), (-8, - 1), (9,5) }

This is not a function because the input 9 has more than one output. (9, 6), (9, 5)

{ (-1,-8), (4,1), (-7,-3), (-3,5) }

This is a function because each input has only one output.

Answer: D does not represent a function hopefully I'm correct with this