@CEWinters You are correct that "ans" is not a supported option for Classic Quiz multiple dropdown quiz questions.  This is currently the only known text value that can't be used with these types of questions though, so if the instructor were to use "ans.", "answer", or even "ans " (adding a space), the question should function as expected.  As far as our engineers are currently aware, there are no other values that would cause this sort of a namespace collision fortunately.