I could register you could register he could register we could register you could register they could register
Forma con V-ing
I could be registering you could be registering he could be registering we could be registering you could be registering they could be registering
Perfecto
I could have registered you could have registered he could have registered we could have registered you could have registered they could have registered
Perfecto con V-ing
I could have been registering you could have been registering he could have been registering we could have been registering you could have been registering they could have been registering
Negación
Forma simple
I could not register you could not register he could not register we could not register you could not register they could not register
Forma con V-ing
I could not be registering you could not be registering he could not be registering we could not be registering you could not be registering they could not be registering
Perfecto
I could not have registered you could not have registered he could not have registered we could not have registered you could not have registered they could not have registered
Perfecto con V-ing
I could not have been registering you could not have been registering he could not have been registering we could not have been registering you could not have been registering they could not have been registering
Forma interrogativa
Forma simple
could I register? could you register? could he register? could we register? could you register? could they register?
Forma con V-ing
could I be registering? could you be registering? could he be registering? could we be registering? could you be registering? could they be registering?
Perfecto
could I have registered? could you have registered? could he have registered? could we have registered? could you have registered? could they have registered?
Perfecto con V-ing
could I have been registering? could you have been registering? could he have been registering? could we have been registering? could you have been registering? could they have been registering?
Forma interro-negativa
Forma simple
could I not register? could you not register? could he not register? could we not register? could you not register? could they not register?
Forma con V-ing
could I not be registering? could you not be registering? could he not be registering? could we not be registering? could you not be registering? could they not be registering?
Perfecto
could I not have registered? could you not have registered? could he not have registered? could we not have registered? could you not have registered? could they not have registered?
Perfecto con V-ing
could I not have been registering? could you not have been registering? could he not have been registering? could we not have been registering? could you not have been registering? could they not have been registering?