I can swim you can swim he can swim we can swim you can swim they can swim
V-ing form
I can be swimming you can be swimming he can be swimming we can be swimming you can be swimming they can be swimming
Perfect
I can have swum you can have swum he can have swum we can have swum you can have swum they can have swum
V-ing perfect
I can have been swimming you can have been swimming he can have been swimming we can have been swimming you can have been swimming they can have been swimming
Negation
Simple form
I cannot swim you cannot swim he cannot swim we cannot swim you cannot swim they cannot swim
V-ing form
I cannot be swimming you cannot be swimming he cannot be swimming we cannot be swimming you cannot be swimming they cannot be swimming
Perfect
I cannot have swum you cannot have swum he cannot have swum we cannot have swum you cannot have swum they cannot have swum
V-ing perfect
I cannot have been swimming you cannot have been swimming he cannot have been swimming we cannot have been swimming you cannot have been swimming they cannot have been swimming
Interrogative form
Simple form
can I swim? can you swim? can he swim? can we swim? can you swim? can they swim?
V-ing form
can I be swimming? can you be swimming? can he be swimming? can we be swimming? can you be swimming? can they be swimming?
Perfect
can I have swum? can you have swum? can he have swum? can we have swum? can you have swum? can they have swum?
V-ing perfect
can I have been swimming? can you have been swimming? can he have been swimming? can we have been swimming? can you have been swimming? can they have been swimming?
Interro-negative form
Simple form
can I not swim? can you not swim? can he not swim? can we not swim? can you not swim? can they not swim?
V-ing form
can I not be swimming? can you not be swimming? can he not be swimming? can we not be swimming? can you not be swimming? can they not be swimming?
Perfect
can I not have swum? can you not have swum? can he not have swum? can we not have swum? can you not have swum? can they not have swum?
V-ing perfect
can I not have been swimming? can you not have been swimming? can he not have been swimming? can we not have been swimming? can you not have been swimming? can they not have been swimming?