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