I could answer you could answer he could answer we could answer you could answer they could answer
Forma com V-ing
I could be answering you could be answering he could be answering we could be answering you could be answering they could be answering
Perfeito
I could have answered you could have answered he could have answered we could have answered you could have answered they could have answered
Perfeito com V-ing
I could have been answering you could have been answering he could have been answering we could have been answering you could have been answering they could have been answering
Negação
Forma simple
I could not answer you could not answer he could not answer we could not answer you could not answer they could not answer
Forma com V-ing
I could not be answering you could not be answering he could not be answering we could not be answering you could not be answering they could not be answering
Perfeito
I could not have answered you could not have answered he could not have answered we could not have answered you could not have answered they could not have answered
Perfeito com V-ing
I could not have been answering you could not have been answering he could not have been answering we could not have been answering you could not have been answering they could not have been answering
Forma interrogativa
Forma simple
could I answer? could you answer? could he answer? could we answer? could you answer? could they answer?
Forma com V-ing
could I be answering? could you be answering? could he be answering? could we be answering? could you be answering? could they be answering?
Perfeito
could I have answered? could you have answered? could he have answered? could we have answered? could you have answered? could they have answered?
Perfeito com V-ing
could I have been answering? could you have been answering? could he have been answering? could we have been answering? could you have been answering? could they have been answering?
Forma interro-Negação
Forma simple
could I not answer? could you not answer? could he not answer? could we not answer? could you not answer? could they not answer?
Forma com V-ing
could I not be answering? could you not be answering? could he not be answering? could we not be answering? could you not be answering? could they not be answering?
Perfeito
could I not have answered? could you not have answered? could he not have answered? could we not have answered? could you not have answered? could they not have answered?
Perfeito com V-ing
could I not have been answering? could you not have been answering? could he not have been answering? could we not have been answering? could you not have been answering? could they not have been answering?