must biff
Verbo regular: biff - biffed- biffed

Afirmación 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
I must biff
you must biff
he must biff
we must biff
you must biff
they must biff 	I must be biffing
you must be biffing
he must be biffing
we must be biffing
you must be biffing
they must be biffing	I must have biffed
you must have biffed
he must have biffed
we must have biffed
you must have biffed
they must have biffed	I must have been biffing
you must have been biffing
he must have been biffing
we must have been biffing
you must have been biffing
they must have been biffing	

Negación 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
I must not biff
you must not biff
he must not biff
we must not biff
you must not biff
they must not biff 	I must not be biffing
you must not be biffing
he must not be biffing
we must not be biffing
you must not be biffing
they must not be biffing	I must not have biffed
you must not have biffed
he must not have biffed
we must not have biffed
you must not have biffed
they must not have biffed	I must not have been biffing
you must not have been biffing
he must not have been biffing
we must not have been biffing
you must not have been biffing
they must not have been biffing	

Forma interrogativa 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
must I biff?
must you biff?
must he biff?
must we biff?
must you biff?
must they biff? 	must I be biffing?
must you be biffing?
must he be biffing?
must we be biffing?
must you be biffing?
must they be biffing? 	must I have biffed?
must you have biffed?
must he have biffed?
must we have biffed?
must you have biffed?
must they have biffed? 	must I have been biffing?
must you have been biffing?
must he have been biffing?
must we have been biffing?
must you have been biffing?
must they have been biffing? 	

Forma interro-negativa 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
must I not biff?
must you not biff?
must he not biff?
must we not biff?
must you not biff?
must they not biff? 	must I not be biffing?
must you not be biffing?
must he not be biffing?
must we not be biffing?
must you not be biffing?
must they not be biffing? 	must I not have biffed?
must you not have biffed?
must he not have biffed?
must we not have biffed?
must you not have biffed?
must they not have biffed? 	must I not have been biffing?
must you not have been biffing?
must he not have been biffing?
must we not have been biffing?
must you not have been biffing?
must they not have been biffing?