must prefer
Regular verb: prefer - preferred- preferred

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I must prefer
you must prefer
she must prefer
we must prefer
you must prefer
they must prefer 	I must be preferring
you must be preferring
she must be preferring
we must be preferring
you must be preferring
they must be preferring	I must have preferred
you must have preferred
she must have preferred
we must have preferred
you must have preferred
they must have preferred	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 	V-ing form 	Perfect 	V-ing perfect 	
I mustn't prefer
you mustn't prefer
she mustn't prefer
we mustn't prefer
you mustn't prefer
they mustn't prefer 	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	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	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 	V-ing form 	Perfect 	V-ing perfect 	
must I prefer?
must you prefer?
must she prefer?
must we prefer?
must you prefer?
must they prefer? 	must I be preferring?
must you be preferring?
must she be preferring?
must we be preferring?
must you be preferring?
must they be preferring? 	must I have preferred?
must you have preferred?
must she have preferred?
must we have preferred?
must you have preferred?
must they have preferred? 	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 	V-ing form 	Perfect 	V-ing perfect 	
mustn't I prefer?
mustn't you prefer?
mustn't she prefer?
mustn't we prefer?
mustn't you prefer?
mustn't they prefer? 	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? 	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? 	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?