I must flap you must flap she must flap we must flap you must flap they must flap
V-ing form
I must be flapping you must be flapping she must be flapping we must be flapping you must be flapping they must be flapping
Perfect
I must have flapped you must have flapped she must have flapped we must have flapped you must have flapped they must have flapped
V-ing perfect
I must have been flapping you must have been flapping she must have been flapping we must have been flapping you must have been flapping they must have been flapping
Negation
Simple form
I mustn't flap you mustn't flap she mustn't flap we mustn't flap you mustn't flap they mustn't flap
V-ing form
I mustn't be flapping you mustn't be flapping she mustn't be flapping we mustn't be flapping you mustn't be flapping they mustn't be flapping
Perfect
I mustn't have flapped you mustn't have flapped she mustn't have flapped we mustn't have flapped you mustn't have flapped they mustn't have flapped
V-ing perfect
I mustn't have been flapping you mustn't have been flapping she mustn't have been flapping we mustn't have been flapping you mustn't have been flapping they mustn't have been flapping
Interrogative form
Simple form
must I flap? must you flap? must she flap? must we flap? must you flap? must they flap?
V-ing form
must I be flapping? must you be flapping? must she be flapping? must we be flapping? must you be flapping? must they be flapping?
Perfect
must I have flapped? must you have flapped? must she have flapped? must we have flapped? must you have flapped? must they have flapped?
V-ing perfect
must I have been flapping? must you have been flapping? must she have been flapping? must we have been flapping? must you have been flapping? must they have been flapping?
Interro-negative form
Simple form
mustn't I flap? mustn't you flap? mustn't she flap? mustn't we flap? mustn't you flap? mustn't they flap?
V-ing form
mustn't I be flapping? mustn't you be flapping? mustn't she be flapping? mustn't we be flapping? mustn't you be flapping? mustn't they be flapping?
Perfect
mustn't I have flapped? mustn't you have flapped? mustn't she have flapped? mustn't we have flapped? mustn't you have flapped? mustn't they have flapped?
V-ing perfect
mustn't I have been flapping? mustn't you have been flapping? mustn't she have been flapping? mustn't we have been flapping? mustn't you have been flapping? mustn't they have been flapping?