I must grimace you must grimace he must grimace we must grimace you must grimace they must grimace
V-ing form
I must be grimacing you must be grimacing he must be grimacing we must be grimacing you must be grimacing they must be grimacing
Perfect
I must have grimaced you must have grimaced he must have grimaced we must have grimaced you must have grimaced they must have grimaced
V-ing perfect
I must have been grimacing you must have been grimacing he must have been grimacing we must have been grimacing you must have been grimacing they must have been grimacing
Negation
Simple form
I must not grimace you must not grimace he must not grimace we must not grimace you must not grimace they must not grimace
V-ing form
I must not be grimacing you must not be grimacing he must not be grimacing we must not be grimacing you must not be grimacing they must not be grimacing
Perfect
I must not have grimaced you must not have grimaced he must not have grimaced we must not have grimaced you must not have grimaced they must not have grimaced
V-ing perfect
I must not have been grimacing you must not have been grimacing he must not have been grimacing we must not have been grimacing you must not have been grimacing they must not have been grimacing
Interrogative form
Simple form
must I grimace? must you grimace? must he grimace? must we grimace? must you grimace? must they grimace?
V-ing form
must I be grimacing? must you be grimacing? must he be grimacing? must we be grimacing? must you be grimacing? must they be grimacing?
Perfect
must I have grimaced? must you have grimaced? must he have grimaced? must we have grimaced? must you have grimaced? must they have grimaced?
V-ing perfect
must I have been grimacing? must you have been grimacing? must he have been grimacing? must we have been grimacing? must you have been grimacing? must they have been grimacing?
Interro-negative form
Simple form
must I not grimace? must you not grimace? must he not grimace? must we not grimace? must you not grimace? must they not grimace?
V-ing form
must I not be grimacing? must you not be grimacing? must he not be grimacing? must we not be grimacing? must you not be grimacing? must they not be grimacing?
Perfect
must I not have grimaced? must you not have grimaced? must he not have grimaced? must we not have grimaced? must you not have grimaced? must they not have grimaced?
V-ing perfect
must I not have been grimacing? must you not have been grimacing? must he not have been grimacing? must we not have been grimacing? must you not have been grimacing? must they not have been grimacing?