I can windsurf you can windsurf he can windsurf we can windsurf you can windsurf they can windsurf
V-ing form
I can be windsurfing you can be windsurfing he can be windsurfing we can be windsurfing you can be windsurfing they can be windsurfing
Perfect
I can have windsurfed you can have windsurfed he can have windsurfed we can have windsurfed you can have windsurfed they can have windsurfed
V-ing perfect
I can have been windsurfing you can have been windsurfing he can have been windsurfing we can have been windsurfing you can have been windsurfing they can have been windsurfing
Negation
Simple form
I cannot windsurf you cannot windsurf he cannot windsurf we cannot windsurf you cannot windsurf they cannot windsurf
V-ing form
I cannot be windsurfing you cannot be windsurfing he cannot be windsurfing we cannot be windsurfing you cannot be windsurfing they cannot be windsurfing
Perfect
I cannot have windsurfed you cannot have windsurfed he cannot have windsurfed we cannot have windsurfed you cannot have windsurfed they cannot have windsurfed
V-ing perfect
I cannot have been windsurfing you cannot have been windsurfing he cannot have been windsurfing we cannot have been windsurfing you cannot have been windsurfing they cannot have been windsurfing
Interrogative form
Simple form
can I windsurf? can you windsurf? can he windsurf? can we windsurf? can you windsurf? can they windsurf?
V-ing form
can I be windsurfing? can you be windsurfing? can he be windsurfing? can we be windsurfing? can you be windsurfing? can they be windsurfing?
Perfect
can I have windsurfed? can you have windsurfed? can he have windsurfed? can we have windsurfed? can you have windsurfed? can they have windsurfed?
V-ing perfect
can I have been windsurfing? can you have been windsurfing? can he have been windsurfing? can we have been windsurfing? can you have been windsurfing? can they have been windsurfing?
Interro-negative form
Simple form
can I not windsurf? can you not windsurf? can he not windsurf? can we not windsurf? can you not windsurf? can they not windsurf?
V-ing form
can I not be windsurfing? can you not be windsurfing? can he not be windsurfing? can we not be windsurfing? can you not be windsurfing? can they not be windsurfing?
Perfect
can I not have windsurfed? can you not have windsurfed? can he not have windsurfed? can we not have windsurfed? can you not have windsurfed? can they not have windsurfed?
V-ing perfect
can I not have been windsurfing? can you not have been windsurfing? can he not have been windsurfing? can we not have been windsurfing? can you not have been windsurfing? can they not have been windsurfing?