c19 is for applying EAD while you dont yet have TPS.
a12 is for ones who's TPS is approved.
so u should choose a12 this time though ur last EAD had c19.

i did quite a bit research regarding reregistration. i m pretty confident it is a12. u can search avvo regarding this. also sajha too. consensus seems to be a12.

u can pretty much ask me any questions regarding TPS. i spent considerable amount of time when i applied for myself.