I could fell you could fell he could fell we could fell you could fell they could fell
V-ing form
I could be felling you could be felling he could be felling we could be felling you could be felling they could be felling
Perfect
I could have felled you could have felled he could have felled we could have felled you could have felled they could have felled
V-ing perfect
I could have been felling you could have been felling he could have been felling we could have been felling you could have been felling they could have been felling
Negation
Simple form
I could not fell you could not fell he could not fell we could not fell you could not fell they could not fell
V-ing form
I could not be felling you could not be felling he could not be felling we could not be felling you could not be felling they could not be felling
Perfect
I could not have felled you could not have felled he could not have felled we could not have felled you could not have felled they could not have felled
V-ing perfect
I could not have been felling you could not have been felling he could not have been felling we could not have been felling you could not have been felling they could not have been felling
Interrogative form
Simple form
could I fell? could you fell? could he fell? could we fell? could you fell? could they fell?
V-ing form
could I be felling? could you be felling? could he be felling? could we be felling? could you be felling? could they be felling?
Perfect
could I have felled? could you have felled? could he have felled? could we have felled? could you have felled? could they have felled?
V-ing perfect
could I have been felling? could you have been felling? could he have been felling? could we have been felling? could you have been felling? could they have been felling?
Interro-negative form
Simple form
could I not fell? could you not fell? could he not fell? could we not fell? could you not fell? could they not fell?
V-ing form
could I not be felling? could you not be felling? could he not be felling? could we not be felling? could you not be felling? could they not be felling?
Perfect
could I not have felled? could you not have felled? could he not have felled? could we not have felled? could you not have felled? could they not have felled?
V-ing perfect
could I not have been felling? could you not have been felling? could he not have been felling? could we not have been felling? could you not have been felling? could they not have been felling?