Answer:
A. For each input value, x, there is exactly one output value, y.
Explanation:
A function always have exactly one output value (y-value) that is related or assigned to each input value (x-value), however, two different x-values can have the same y-value.
In the graph given, although two different values have the same y-value, every x-value has exactly one y-value corresponding to it. No x-value has two different y-values.
Therefore, the graph represents a function.