I can fire you can fire he can fire we can fire you can fire they can fire
V-ing form
I can be firing you can be firing he can be firing we can be firing you can be firing they can be firing
Perfect
I can have fired you can have fired he can have fired we can have fired you can have fired they can have fired
V-ing perfect
I can have been firing you can have been firing he can have been firing we can have been firing you can have been firing they can have been firing
Negation
Simple form
I cannot fire you cannot fire he cannot fire we cannot fire you cannot fire they cannot fire
V-ing form
I cannot be firing you cannot be firing he cannot be firing we cannot be firing you cannot be firing they cannot be firing
Perfect
I cannot have fired you cannot have fired he cannot have fired we cannot have fired you cannot have fired they cannot have fired
V-ing perfect
I cannot have been firing you cannot have been firing he cannot have been firing we cannot have been firing you cannot have been firing they cannot have been firing
Interrogative form
Simple form
can I fire? can you fire? can he fire? can we fire? can you fire? can they fire?
V-ing form
can I be firing? can you be firing? can he be firing? can we be firing? can you be firing? can they be firing?
Perfect
can I have fired? can you have fired? can he have fired? can we have fired? can you have fired? can they have fired?
V-ing perfect
can I have been firing? can you have been firing? can he have been firing? can we have been firing? can you have been firing? can they have been firing?
Interro-negative form
Simple form
can I not fire? can you not fire? can he not fire? can we not fire? can you not fire? can they not fire?
V-ing form
can I not be firing? can you not be firing? can he not be firing? can we not be firing? can you not be firing? can they not be firing?
Perfect
can I not have fired? can you not have fired? can he not have fired? can we not have fired? can you not have fired? can they not have fired?
V-ing perfect
can I not have been firing? can you not have been firing? can he not have been firing? can we not have been firing? can you not have been firing? can they not have been firing?