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