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 couldn't forge you couldn't forge he couldn't forge we couldn't forge you couldn't forge they couldn't forge
V-ing form
I couldn't be forging you couldn't be forging he couldn't be forging we couldn't be forging you couldn't be forging they couldn't be forging
Perfect
I couldn't have forged you couldn't have forged he couldn't have forged we couldn't have forged you couldn't have forged they couldn't have forged
V-ing perfect
I couldn't have been forging you couldn't have been forging he couldn't have been forging we couldn't have been forging you couldn't have been forging they couldn't 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
couldn't I forge? couldn't you forge? couldn't he forge? couldn't we forge? couldn't you forge? couldn't they forge?
V-ing form
couldn't I be forging? couldn't you be forging? couldn't he be forging? couldn't we be forging? couldn't you be forging? couldn't they be forging?
Perfect
couldn't I have forged? couldn't you have forged? couldn't he have forged? couldn't we have forged? couldn't you have forged? couldn't they have forged?
V-ing perfect
couldn't I have been forging? couldn't you have been forging? couldn't he have been forging? couldn't we have been forging? couldn't you have been forging? couldn't they have been forging?