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