I could forge you could forge he could forge we could forge you could forge they could forge
V-ing form
I could be forging you could be forging he could be forging we could be forging you could be forging they could be forging
Perfect
I could have forged you could have forged he could have forged we could have forged you could have forged they could have forged
V-ing perfect
I could have been forging you could have been forging he could have been forging we could have been forging you could have been forging they could have been forging
Negation
Simple form
I could not forge you could not forge he could not forge we could not forge you could not forge they could not forge
V-ing form
I could not be forging you could not be forging he could not be forging we could not be forging you could not be forging they could not be forging
Perfect
I could not have forged you could not have forged he could not have forged we could not have forged you could not have forged they could not have forged
V-ing perfect
I could not have been forging you could not have been forging he could not have been forging we could not have been forging you could not have been forging they could not have been forging
Interrogative form
Simple form
could I forge? could you forge? could he forge? could we forge? could you forge? could they forge?
V-ing form
could I be forging? could you be forging? could he be forging? could we be forging? could you be forging? could they be forging?
Perfect
could I have forged? could you have forged? could he have forged? could we have forged? could you have forged? could they have forged?
V-ing perfect
could I have been forging? could you have been forging? could he have been forging? could we have been forging? could you have been forging? could they have been forging?
Interro-negative form
Simple form
could I not forge? could you not forge? could he not forge? could we not forge? could you not forge? could they not forge?
V-ing form
could I not be forging? could you not be forging? could he not be forging? could we not be forging? could you not be forging? could they not be forging?
Perfect
could I not have forged? could you not have forged? could he not have forged? could we not have forged? could you not have forged? could they not have forged?
V-ing perfect
could I not have been forging? could you not have been forging? could he not have been forging? could we not have been forging? could you not have been forging? could they not have been forging?