I could master you could master he could master we could master you could master they could master
Forma con V-ing
I could be mastering you could be mastering he could be mastering we could be mastering you could be mastering they could be mastering
Perfecto
I could have mastered you could have mastered he could have mastered we could have mastered you could have mastered they could have mastered
Perfecto con V-ing
I could have been mastering you could have been mastering he could have been mastering we could have been mastering you could have been mastering they could have been mastering
Negación
Forma simple
I could not master you could not master he could not master we could not master you could not master they could not master
Forma con V-ing
I could not be mastering you could not be mastering he could not be mastering we could not be mastering you could not be mastering they could not be mastering
Perfecto
I could not have mastered you could not have mastered he could not have mastered we could not have mastered you could not have mastered they could not have mastered
Perfecto con V-ing
I could not have been mastering you could not have been mastering he could not have been mastering we could not have been mastering you could not have been mastering they could not have been mastering
Forma interrogativa
Forma simple
could I master? could you master? could he master? could we master? could you master? could they master?
Forma con V-ing
could I be mastering? could you be mastering? could he be mastering? could we be mastering? could you be mastering? could they be mastering?
Perfecto
could I have mastered? could you have mastered? could he have mastered? could we have mastered? could you have mastered? could they have mastered?
Perfecto con V-ing
could I have been mastering? could you have been mastering? could he have been mastering? could we have been mastering? could you have been mastering? could they have been mastering?
Forma interro-negativa
Forma simple
could I not master? could you not master? could he not master? could we not master? could you not master? could they not master?
Forma con V-ing
could I not be mastering? could you not be mastering? could he not be mastering? could we not be mastering? could you not be mastering? could they not be mastering?
Perfecto
could I not have mastered? could you not have mastered? could he not have mastered? could we not have mastered? could you not have mastered? could they not have mastered?
Perfecto con V-ing
could I not have been mastering? could you not have been mastering? could he not have been mastering? could we not have been mastering? could you not have been mastering? could they not have been mastering?