I can walk you can walk he can walk we can walk you can walk they can walk
V-ing form
I can be walking you can be walking he can be walking we can be walking you can be walking they can be walking
Perfect
I can have walked you can have walked he can have walked we can have walked you can have walked they can have walked
V-ing perfect
I can have been walking you can have been walking he can have been walking we can have been walking you can have been walking they can have been walking
Negation
Simple form
I cannot walk you cannot walk he cannot walk we cannot walk you cannot walk they cannot walk
V-ing form
I cannot be walking you cannot be walking he cannot be walking we cannot be walking you cannot be walking they cannot be walking
Perfect
I cannot have walked you cannot have walked he cannot have walked we cannot have walked you cannot have walked they cannot have walked
V-ing perfect
I cannot have been walking you cannot have been walking he cannot have been walking we cannot have been walking you cannot have been walking they cannot have been walking
Interrogative form
Simple form
can I walk? can you walk? can he walk? can we walk? can you walk? can they walk?
V-ing form
can I be walking? can you be walking? can he be walking? can we be walking? can you be walking? can they be walking?
Perfect
can I have walked? can you have walked? can he have walked? can we have walked? can you have walked? can they have walked?
V-ing perfect
can I have been walking? can you have been walking? can he have been walking? can we have been walking? can you have been walking? can they have been walking?
Interro-negative form
Simple form
can I not walk? can you not walk? can he not walk? can we not walk? can you not walk? can they not walk?
V-ing form
can I not be walking? can you not be walking? can he not be walking? can we not be walking? can you not be walking? can they not be walking?
Perfect
can I not have walked? can you not have walked? can he not have walked? can we not have walked? can you not have walked? can they not have walked?
V-ing perfect
can I not have been walking? can you not have been walking? can he not have been walking? can we not have been walking? can you not have been walking? can they not have been walking?