ANSWER:
Yes, it is a function
Explanation:
We must take into account the difference between relation and function to know if it is a function or not. Therefore, we have to:
A relation is a correspondence of elements between two sets.
A function is a relation where each element of a set (Input values) corresponds to one and only one element of another set (Output values).
Therefore, a function is a relation to which the condition is added that each value of the domain corresponds to one and only one value of the path.
We can see from the graph that each input value corresponds to a single output value.