domain is the numbers you can use for x
so if the domain is all real numbers except -2, then subsituting -2 for x will result in an undefined like division by 0 or square root of a negative
subsituting it into the first one give us

which is undefined, that's the answer
2nd one, gives us -4
3rd gives us -6
4th gives us

which is also undefined
well, 2 possible answers, none are the best, they are both undefined