I can scratch you can scratch he can scratch we can scratch you can scratch they can scratch
V-ing form
I can be scratching you can be scratching he can be scratching we can be scratching you can be scratching they can be scratching
Perfect
I can have scratched you can have scratched he can have scratched we can have scratched you can have scratched they can have scratched
V-ing perfect
I can have been scratching you can have been scratching he can have been scratching we can have been scratching you can have been scratching they can have been scratching
Negation
Simple form
I can't scratch you can't scratch he can't scratch we can't scratch you can't scratch they can't scratch
V-ing form
I can't be scratching you can't be scratching he can't be scratching we can't be scratching you can't be scratching they can't be scratching
Perfect
I can't have scratched you can't have scratched he can't have scratched we can't have scratched you can't have scratched they can't have scratched
V-ing perfect
I can't have been scratching you can't have been scratching he can't have been scratching we can't have been scratching you can't have been scratching they can't have been scratching
Interrogative form
Simple form
can I scratch? can you scratch? can he scratch? can we scratch? can you scratch? can they scratch?
V-ing form
can I be scratching? can you be scratching? can he be scratching? can we be scratching? can you be scratching? can they be scratching?
Perfect
can I have scratched? can you have scratched? can he have scratched? can we have scratched? can you have scratched? can they have scratched?
V-ing perfect
can I have been scratching? can you have been scratching? can he have been scratching? can we have been scratching? can you have been scratching? can they have been scratching?
Interro-negative form
Simple form
can't I scratch? can't you scratch? can't he scratch? can't we scratch? can't you scratch? can't they scratch?
V-ing form
can't I be scratching? can't you be scratching? can't he be scratching? can't we be scratching? can't you be scratching? can't they be scratching?
Perfect
can't I have scratched? can't you have scratched? can't he have scratched? can't we have scratched? can't you have scratched? can't they have scratched?
V-ing perfect
can't I have been scratching? can't you have been scratching? can't he have been scratching? can't we have been scratching? can't you have been scratching? can't they have been scratching?