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