I must breathe you must breathe he must breathe we must breathe you must breathe they must breathe
V-ing form
I must be breathing you must be breathing he must be breathing we must be breathing you must be breathing they must be breathing
Perfect
I must have breathed you must have breathed he must have breathed we must have breathed you must have breathed they must have breathed
V-ing perfect
I must have been breathing you must have been breathing he must have been breathing we must have been breathing you must have been breathing they must have been breathing
Negation
Simple form
I must not breathe you must not breathe he must not breathe we must not breathe you must not breathe they must not breathe
V-ing form
I must not be breathing you must not be breathing he must not be breathing we must not be breathing you must not be breathing they must not be breathing
Perfect
I must not have breathed you must not have breathed he must not have breathed we must not have breathed you must not have breathed they must not have breathed
V-ing perfect
I must not have been breathing you must not have been breathing he must not have been breathing we must not have been breathing you must not have been breathing they must not have been breathing
Interrogative form
Simple form
must I breathe? must you breathe? must he breathe? must we breathe? must you breathe? must they breathe?
V-ing form
must I be breathing? must you be breathing? must he be breathing? must we be breathing? must you be breathing? must they be breathing?
Perfect
must I have breathed? must you have breathed? must he have breathed? must we have breathed? must you have breathed? must they have breathed?
V-ing perfect
must I have been breathing? must you have been breathing? must he have been breathing? must we have been breathing? must you have been breathing? must they have been breathing?
Interro-negative form
Simple form
must I not breathe? must you not breathe? must he not breathe? must we not breathe? must you not breathe? must they not breathe?
V-ing form
must I not be breathing? must you not be breathing? must he not be breathing? must we not be breathing? must you not be breathing? must they not be breathing?
Perfect
must I not have breathed? must you not have breathed? must he not have breathed? must we not have breathed? must you not have breathed? must they not have breathed?
V-ing perfect
must I not have been breathing? must you not have been breathing? must he not have been breathing? must we not have been breathing? must you not have been breathing? must they not have been breathing?