I can flex you can flex he can flex we can flex you can flex they can flex
V-ing form
I can be flexing you can be flexing he can be flexing we can be flexing you can be flexing they can be flexing
Perfect
I can have flexed you can have flexed he can have flexed we can have flexed you can have flexed they can have flexed
V-ing perfect
I can have been flexing you can have been flexing he can have been flexing we can have been flexing you can have been flexing they can have been flexing
Negation
Simple form
I cannot flex you cannot flex he cannot flex we cannot flex you cannot flex they cannot flex
V-ing form
I cannot be flexing you cannot be flexing he cannot be flexing we cannot be flexing you cannot be flexing they cannot be flexing
Perfect
I cannot have flexed you cannot have flexed he cannot have flexed we cannot have flexed you cannot have flexed they cannot have flexed
V-ing perfect
I cannot have been flexing you cannot have been flexing he cannot have been flexing we cannot have been flexing you cannot have been flexing they cannot have been flexing
Interrogative form
Simple form
can I flex? can you flex? can he flex? can we flex? can you flex? can they flex?
V-ing form
can I be flexing? can you be flexing? can he be flexing? can we be flexing? can you be flexing? can they be flexing?
Perfect
can I have flexed? can you have flexed? can he have flexed? can we have flexed? can you have flexed? can they have flexed?
V-ing perfect
can I have been flexing? can you have been flexing? can he have been flexing? can we have been flexing? can you have been flexing? can they have been flexing?
Interro-negative form
Simple form
can I not flex? can you not flex? can he not flex? can we not flex? can you not flex? can they not flex?
V-ing form
can I not be flexing? can you not be flexing? can he not be flexing? can we not be flexing? can you not be flexing? can they not be flexing?
Perfect
can I not have flexed? can you not have flexed? can he not have flexed? can we not have flexed? can you not have flexed? can they not have flexed?
V-ing perfect
can I not have been flexing? can you not have been flexing? can he not have been flexing? can we not have been flexing? can you not have been flexing? can they not have been flexing?