Answer: Fourth option.
Step-by-step explanation:
By definition, a relationship is a function if and only if each input value (or each x-value) has only one output value (or y-value).
Given the first table:
You can notice that the input values 2 and 3 do not have only one output value. Therefore, this table does not represent a function.
The second table is:
You can notice that the input values 4 and -4 do not have only one output value. Therefore, this table does not represent a function.
The third table is:
You can notice that the input values 6 and 7 do not have only one output value. Therefore, this table does not represent a function.
The fourth table is:
You can notice that each input value has only one output value. Therefore, this table represents a function.