ANSWER

Step-by-step explanation
The given set of ordered pairs for the function is

If Isaac must create one more pair so that the set will still be a function, then he can only add a point whose x-coordinate has not already occurred in the set.
The reason is that, a function must not have an x-value that has many y-values.
Among the given options, the only point whose first coordinate has not already occurred in the ordered pairs is

Therefore the correct answer is option 2.