The input value 0 will complete the table for us to have the relation as a function
For a relation to be a function, no two output must have the same input
Looking at the table, we already have the values 2,3,7 and 10
For us to have a function, the option we are to select will be different from the ones already listed
The only value differeny from the ones already listed is 0 and this is our answer