I could well you could well he could well we could well you could well they could well
V-ing form
I could be welling you could be welling he could be welling we could be welling you could be welling they could be welling
Perfect
I could have welled you could have welled he could have welled we could have welled you could have welled they could have welled
V-ing perfect
I could have been welling you could have been welling he could have been welling we could have been welling you could have been welling they could have been welling
Negation
Simple form
I couldn't well you couldn't well he couldn't well we couldn't well you couldn't well they couldn't well
V-ing form
I couldn't be welling you couldn't be welling he couldn't be welling we couldn't be welling you couldn't be welling they couldn't be welling
Perfect
I couldn't have welled you couldn't have welled he couldn't have welled we couldn't have welled you couldn't have welled they couldn't have welled
V-ing perfect
I couldn't have been welling you couldn't have been welling he couldn't have been welling we couldn't have been welling you couldn't have been welling they couldn't have been welling
Interrogative form
Simple form
could I well? could you well? could he well? could we well? could you well? could they well?
V-ing form
could I be welling? could you be welling? could he be welling? could we be welling? could you be welling? could they be welling?
Perfect
could I have welled? could you have welled? could he have welled? could we have welled? could you have welled? could they have welled?
V-ing perfect
could I have been welling? could you have been welling? could he have been welling? could we have been welling? could you have been welling? could they have been welling?
Interro-negative form
Simple form
couldn't I well? couldn't you well? couldn't he well? couldn't we well? couldn't you well? couldn't they well?
V-ing form
couldn't I be welling? couldn't you be welling? couldn't he be welling? couldn't we be welling? couldn't you be welling? couldn't they be welling?
Perfect
couldn't I have welled? couldn't you have welled? couldn't he have welled? couldn't we have welled? couldn't you have welled? couldn't they have welled?
V-ing perfect
couldn't I have been welling? couldn't you have been welling? couldn't he have been welling? couldn't we have been welling? couldn't you have been welling? couldn't they have been welling?