I can function you can function he can function we can function you can function they can function
V-ing form
I can be functioning you can be functioning he can be functioning we can be functioning you can be functioning they can be functioning
Perfect
I can have functioned you can have functioned he can have functioned we can have functioned you can have functioned they can have functioned
V-ing perfect
I can have been functioning you can have been functioning he can have been functioning we can have been functioning you can have been functioning they can have been functioning
Negation
Simple form
I can't function you can't function he can't function we can't function you can't function they can't function
V-ing form
I can't be functioning you can't be functioning he can't be functioning we can't be functioning you can't be functioning they can't be functioning
Perfect
I can't have functioned you can't have functioned he can't have functioned we can't have functioned you can't have functioned they can't have functioned
V-ing perfect
I can't have been functioning you can't have been functioning he can't have been functioning we can't have been functioning you can't have been functioning they can't have been functioning
Interrogative form
Simple form
can I function? can you function? can he function? can we function? can you function? can they function?
V-ing form
can I be functioning? can you be functioning? can he be functioning? can we be functioning? can you be functioning? can they be functioning?
Perfect
can I have functioned? can you have functioned? can he have functioned? can we have functioned? can you have functioned? can they have functioned?
V-ing perfect
can I have been functioning? can you have been functioning? can he have been functioning? can we have been functioning? can you have been functioning? can they have been functioning?
Interro-negative form
Simple form
can't I function? can't you function? can't he function? can't we function? can't you function? can't they function?
V-ing form
can't I be functioning? can't you be functioning? can't he be functioning? can't we be functioning? can't you be functioning? can't they be functioning?
Perfect
can't I have functioned? can't you have functioned? can't he have functioned? can't we have functioned? can't you have functioned? can't they have functioned?
V-ing perfect
can't I have been functioning? can't you have been functioning? can't he have been functioning? can't we have been functioning? can't you have been functioning? can't they have been functioning?