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 can't walk you can't walk he can't walk we can't walk you can't walk they can't walk
V-ing form
I can't be walking you can't be walking he can't be walking we can't be walking you can't be walking they can't be walking
Perfect
I can't have walked you can't have walked he can't have walked we can't have walked you can't have walked they can't have walked
V-ing perfect
I can't have been walking you can't have been walking he can't have been walking we can't have been walking you can't have been walking they can't 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't I walk? can't you walk? can't he walk? can't we walk? can't you walk? can't they walk?
V-ing form
can't I be walking? can't you be walking? can't he be walking? can't we be walking? can't you be walking? can't they be walking?
Perfect
can't I have walked? can't you have walked? can't he have walked? can't we have walked? can't you have walked? can't they have walked?
V-ing perfect
can't I have been walking? can't you have been walking? can't he have been walking? can't we have been walking? can't you have been walking? can't they have been walking?