I could sum you could sum she could sum we could sum you could sum they could sum
Forma con V-ing
I could be summing you could be summing she could be summing we could be summing you could be summing they could be summing
Perfecto
I could have summed you could have summed she could have summed we could have summed you could have summed they could have summed
Perfecto con V-ing
I could have been summing you could have been summing she could have been summing we could have been summing you could have been summing they could have been summing
Negación
Forma simple
I couldn't sum you couldn't sum she couldn't sum we couldn't sum you couldn't sum they couldn't sum
Forma con V-ing
I couldn't be summing you couldn't be summing she couldn't be summing we couldn't be summing you couldn't be summing they couldn't be summing
Perfecto
I couldn't have summed you couldn't have summed she couldn't have summed we couldn't have summed you couldn't have summed they couldn't have summed
Perfecto con V-ing
I couldn't have been summing you couldn't have been summing she couldn't have been summing we couldn't have been summing you couldn't have been summing they couldn't have been summing
Forma interrogativa
Forma simple
could I sum? could you sum? could she sum? could we sum? could you sum? could they sum?
Forma con V-ing
could I be summing? could you be summing? could she be summing? could we be summing? could you be summing? could they be summing?
Perfecto
could I have summed? could you have summed? could she have summed? could we have summed? could you have summed? could they have summed?
Perfecto con V-ing
could I have been summing? could you have been summing? could she have been summing? could we have been summing? could you have been summing? could they have been summing?
Forma interro-negativa
Forma simple
couldn't I sum? couldn't you sum? couldn't she sum? couldn't we sum? couldn't you sum? couldn't they sum?
Forma con V-ing
couldn't I be summing? couldn't you be summing? couldn't she be summing? couldn't we be summing? couldn't you be summing? couldn't they be summing?
Perfecto
couldn't I have summed? couldn't you have summed? couldn't she have summed? couldn't we have summed? couldn't you have summed? couldn't they have summed?
Perfecto con V-ing
couldn't I have been summing? couldn't you have been summing? couldn't she have been summing? couldn't we have been summing? couldn't you have been summing? couldn't they have been summing?