I can swim you can swim she can swim we can swim you can swim they can swim
V-ing form
I can be swimming you can be swimming she can be swimming we can be swimming you can be swimming they can be swimming
Perfect
I can have swum you can have swum she 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 she 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 she cannot swim we cannot swim you cannot swim they cannot swim
V-ing form
I cannot be swimming you cannot be swimming she cannot be swimming we cannot be swimming you cannot be swimming they cannot be swimming
Perfect
I cannot have swum you cannot have swum she 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 she 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 she swim? can we swim? can you swim? can they swim?
V-ing form
can I be swimming? can you be swimming? can she be swimming? can we be swimming? can you be swimming? can they be swimming?
Perfect
can I have swum? can you have swum? can she 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 she 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 she 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 she 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 she 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 she not have been swimming? can we not have been swimming? can you not have been swimming? can they not have been swimming?