I must collapse you must collapse he must collapse we must collapse you must collapse they must collapse
V-ing form
I must be collapsing you must be collapsing he must be collapsing we must be collapsing you must be collapsing they must be collapsing
Perfect
I must have collapsed you must have collapsed he must have collapsed we must have collapsed you must have collapsed they must have collapsed
V-ing perfect
I must have been collapsing you must have been collapsing he must have been collapsing we must have been collapsing you must have been collapsing they must have been collapsing
Negation
Simple form
I mustn't collapse you mustn't collapse he mustn't collapse we mustn't collapse you mustn't collapse they mustn't collapse
V-ing form
I mustn't be collapsing you mustn't be collapsing he mustn't be collapsing we mustn't be collapsing you mustn't be collapsing they mustn't be collapsing
Perfect
I mustn't have collapsed you mustn't have collapsed he mustn't have collapsed we mustn't have collapsed you mustn't have collapsed they mustn't have collapsed
V-ing perfect
I mustn't have been collapsing you mustn't have been collapsing he mustn't have been collapsing we mustn't have been collapsing you mustn't have been collapsing they mustn't have been collapsing
Interrogative form
Simple form
must I collapse? must you collapse? must he collapse? must we collapse? must you collapse? must they collapse?
V-ing form
must I be collapsing? must you be collapsing? must he be collapsing? must we be collapsing? must you be collapsing? must they be collapsing?
Perfect
must I have collapsed? must you have collapsed? must he have collapsed? must we have collapsed? must you have collapsed? must they have collapsed?
V-ing perfect
must I have been collapsing? must you have been collapsing? must he have been collapsing? must we have been collapsing? must you have been collapsing? must they have been collapsing?
Interro-negative form
Simple form
mustn't I collapse? mustn't you collapse? mustn't he collapse? mustn't we collapse? mustn't you collapse? mustn't they collapse?
V-ing form
mustn't I be collapsing? mustn't you be collapsing? mustn't he be collapsing? mustn't we be collapsing? mustn't you be collapsing? mustn't they be collapsing?
Perfect
mustn't I have collapsed? mustn't you have collapsed? mustn't he have collapsed? mustn't we have collapsed? mustn't you have collapsed? mustn't they have collapsed?
V-ing perfect
mustn't I have been collapsing? mustn't you have been collapsing? mustn't he have been collapsing? mustn't we have been collapsing? mustn't you have been collapsing? mustn't they have been collapsing?