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