Answer:
D
Explanation:
Each x value can have only ONE y value
this means that there cannot be more than one of the same x value:
think of the x values as an input, each input has one output right?
ex:
input: 7
output:8
input:3
output:2
how is it possible that the same input has different outputs?
input: 5
output: 6,7
this does not make any sense, one input should only have one output hence, one value of x(input) should have only one value of y(output)
Hope this helps!