For something to be a function, the input (x value) can only have one output (y value). If an x value has more than one y value, it is not a function.
A.) When x = 1, it has 5 y values. This is not a function
B.) -2 and -1 have two y values. This is not a function
C.) 1 and 2 have two y values. This is not a function
D.) Each input has only one output. This is a function. (Inputs can share the same outputs)
Your answer is D
