////The answer is D and the number is 30.

A says, "It's two digits." The number would have to be 100 or more, and B could not be true.
B says, "It goes evenly into 150." If this is untrue, D could also not be true.
C says, "It is not 150." If this is untrue 150, or A would also not be true.////

Correct.

////B is lying and the number is 50/////

If B is lying then either A or D would also have to be lying and only one person is lying.