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