I can fight you can fight he can fight we can fight you can fight they can fight
V-ing form
I can be fighting you can be fighting he can be fighting we can be fighting you can be fighting they can be fighting
Perfect
I can have fought you can have fought he can have fought we can have fought you can have fought they can have fought
V-ing perfect
I can have been fighting you can have been fighting he can have been fighting we can have been fighting you can have been fighting they can have been fighting
Negation
Simple form
I cannot fight you cannot fight he cannot fight we cannot fight you cannot fight they cannot fight
V-ing form
I cannot be fighting you cannot be fighting he cannot be fighting we cannot be fighting you cannot be fighting they cannot be fighting
Perfect
I cannot have fought you cannot have fought he cannot have fought we cannot have fought you cannot have fought they cannot have fought
V-ing perfect
I cannot have been fighting you cannot have been fighting he cannot have been fighting we cannot have been fighting you cannot have been fighting they cannot have been fighting
Interrogative form
Simple form
can I fight? can you fight? can he fight? can we fight? can you fight? can they fight?
V-ing form
can I be fighting? can you be fighting? can he be fighting? can we be fighting? can you be fighting? can they be fighting?
Perfect
can I have fought? can you have fought? can he have fought? can we have fought? can you have fought? can they have fought?
V-ing perfect
can I have been fighting? can you have been fighting? can he have been fighting? can we have been fighting? can you have been fighting? can they have been fighting?
Interro-negative form
Simple form
can I not fight? can you not fight? can he not fight? can we not fight? can you not fight? can they not fight?
V-ing form
can I not be fighting? can you not be fighting? can he not be fighting? can we not be fighting? can you not be fighting? can they not be fighting?
Perfect
can I not have fought? can you not have fought? can he not have fought? can we not have fought? can you not have fought? can they not have fought?
V-ing perfect
can I not have been fighting? can you not have been fighting? can he not have been fighting? can we not have been fighting? can you not have been fighting? can they not have been fighting?