the second choice, and the last choice are correct.
the first one, x can be any number.
the second one, x can be any number but not -1(the denominator cannot be 0)
the third one, x has to be ≥ 1/2, because 2x-1 cannot be negative.
the fourth one, x can be any number but not -1 or -4
the last one, x can be any number but not -3
