I can sleep you can sleep she can sleep we can sleep you can sleep they can sleep
V-ing form
I can be sleeping you can be sleeping she can be sleeping we can be sleeping you can be sleeping they can be sleeping
Perfect
I can have slept you can have slept she can have slept we can have slept you can have slept they can have slept
V-ing perfect
I can have been sleeping you can have been sleeping she can have been sleeping we can have been sleeping you can have been sleeping they can have been sleeping
Negation
Simple form
I cannot sleep you cannot sleep she cannot sleep we cannot sleep you cannot sleep they cannot sleep
V-ing form
I cannot be sleeping you cannot be sleeping she cannot be sleeping we cannot be sleeping you cannot be sleeping they cannot be sleeping
Perfect
I cannot have slept you cannot have slept she cannot have slept we cannot have slept you cannot have slept they cannot have slept
V-ing perfect
I cannot have been sleeping you cannot have been sleeping she cannot have been sleeping we cannot have been sleeping you cannot have been sleeping they cannot have been sleeping
Interrogative form
Simple form
can I sleep? can you sleep? can she sleep? can we sleep? can you sleep? can they sleep?
V-ing form
can I be sleeping? can you be sleeping? can she be sleeping? can we be sleeping? can you be sleeping? can they be sleeping?
Perfect
can I have slept? can you have slept? can she have slept? can we have slept? can you have slept? can they have slept?
V-ing perfect
can I have been sleeping? can you have been sleeping? can she have been sleeping? can we have been sleeping? can you have been sleeping? can they have been sleeping?
Interro-negative form
Simple form
can I not sleep? can you not sleep? can she not sleep? can we not sleep? can you not sleep? can they not sleep?
V-ing form
can I not be sleeping? can you not be sleeping? can she not be sleeping? can we not be sleeping? can you not be sleeping? can they not be sleeping?
Perfect
can I not have slept? can you not have slept? can she not have slept? can we not have slept? can you not have slept? can they not have slept?
V-ing perfect
can I not have been sleeping? can you not have been sleeping? can she not have been sleeping? can we not have been sleeping? can you not have been sleeping? can they not have been sleeping?