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