A function can be a one to one or a many to one function. For a one to one function, there is only one value of y for one value of x. For a many to one function, there are many avlues of x to one value of y. If a value of x has more than one value of y, then it is not a function
looking at the given tables,
The function is the first option because there is only one value of x for a value of y
x y
2 2
3 3
4 4
5 5
6 6