I could stack you could stack he could stack we could stack you could stack they could stack
Forma con V-ing
I could be stacking you could be stacking he could be stacking we could be stacking you could be stacking they could be stacking
Perfecto
I could have stacked you could have stacked he could have stacked we could have stacked you could have stacked they could have stacked
Perfecto con V-ing
I could have been stacking you could have been stacking he could have been stacking we could have been stacking you could have been stacking they could have been stacking
Negación
Forma simple
I could not stack you could not stack he could not stack we could not stack you could not stack they could not stack
Forma con V-ing
I could not be stacking you could not be stacking he could not be stacking we could not be stacking you could not be stacking they could not be stacking
Perfecto
I could not have stacked you could not have stacked he could not have stacked we could not have stacked you could not have stacked they could not have stacked
Perfecto con V-ing
I could not have been stacking you could not have been stacking he could not have been stacking we could not have been stacking you could not have been stacking they could not have been stacking
Forma interrogativa
Forma simple
could I stack? could you stack? could he stack? could we stack? could you stack? could they stack?
Forma con V-ing
could I be stacking? could you be stacking? could he be stacking? could we be stacking? could you be stacking? could they be stacking?
Perfecto
could I have stacked? could you have stacked? could he have stacked? could we have stacked? could you have stacked? could they have stacked?
Perfecto con V-ing
could I have been stacking? could you have been stacking? could he have been stacking? could we have been stacking? could you have been stacking? could they have been stacking?
Forma interro-negativa
Forma simple
could I not stack? could you not stack? could he not stack? could we not stack? could you not stack? could they not stack?
Forma con V-ing
could I not be stacking? could you not be stacking? could he not be stacking? could we not be stacking? could you not be stacking? could they not be stacking?
Perfecto
could I not have stacked? could you not have stacked? could he not have stacked? could we not have stacked? could you not have stacked? could they not have stacked?
Perfecto con V-ing
could I not have been stacking? could you not have been stacking? could he not have been stacking? could we not have been stacking? could you not have been stacking? could they not have been stacking?