1. The problem statement, all variables and given/known data The quantum numbers +1/2 and -1/2 for the electron spin represents? 2. Relevant equations a) rotation of electron in clockwise and anticlockwise directions respectively b) tow quantum mechanical spin states which have no classical analogue c) Magnetic moment of electron pointing up and down respectively d) Rotation of electron in anticlockwise and clockwise directions respectively 3. The attempt at a solution Since the term "respectively" is used in the options a) and d), the option d) cancels out and even i think the option c cancels out also. I am confused between the a) and b) one, what does one mean by classical analogue?