I must flex you must flex she must flex we must flex you must flex they must flex
V-ing form
I must be flexing you must be flexing she must be flexing we must be flexing you must be flexing they must be flexing
Perfect
I must have flexed you must have flexed she 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 she 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 she 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 she 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 she 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 she 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 she flex? must we flex? must you flex? must they flex?
V-ing form
must I be flexing? must you be flexing? must she be flexing? must we be flexing? must you be flexing? must they be flexing?
Perfect
must I have flexed? must you have flexed? must she 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 she 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 she 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 she 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 she 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 she not have been flexing? must we not have been flexing? must you not have been flexing? must they not have been flexing?