The quantum numbers +1/2 and -1/2 for the electron spin represent :

The quantum numbers +1/2 and -1/2 for the electron spin represent two quantum mechanical spin states which have no classical analogue

There are two non-classical quantum mechanical spin states.
Similar to how the earth revolves around the sun while spinning on its own axis, an electron too revolves around its own axis. In other words, an electron possesses inherent spin angular quantum number in addition to charge and mass. The electron's spin angular momentum can be oriented in one of two directions with respect to the selected axis. The spin quantum numbers, which might have values of $+1/2$ or $-1/2$, serve to differentiate these two orientations.
There is no classical analogue to electron spin.
The correct option is D