must fib
Regular verb: fib - fibbed- fibbed

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I must fib
you must fib
she must fib
we must fib
you must fib
they must fib 	I must be fibbing
you must be fibbing
she must be fibbing
we must be fibbing
you must be fibbing
they must be fibbing	I must have fibbed
you must have fibbed
she must have fibbed
we must have fibbed
you must have fibbed
they must have fibbed	I must have been fibbing
you must have been fibbing
she must have been fibbing
we must have been fibbing
you must have been fibbing
they must have been fibbing	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I mustn't fib
you mustn't fib
she mustn't fib
we mustn't fib
you mustn't fib
they mustn't fib 	I mustn't be fibbing
you mustn't be fibbing
she mustn't be fibbing
we mustn't be fibbing
you mustn't be fibbing
they mustn't be fibbing	I mustn't have fibbed
you mustn't have fibbed
she mustn't have fibbed
we mustn't have fibbed
you mustn't have fibbed
they mustn't have fibbed	I mustn't have been fibbing
you mustn't have been fibbing
she mustn't have been fibbing
we mustn't have been fibbing
you mustn't have been fibbing
they mustn't have been fibbing	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
must I fib?
must you fib?
must she fib?
must we fib?
must you fib?
must they fib? 	must I be fibbing?
must you be fibbing?
must she be fibbing?
must we be fibbing?
must you be fibbing?
must they be fibbing? 	must I have fibbed?
must you have fibbed?
must she have fibbed?
must we have fibbed?
must you have fibbed?
must they have fibbed? 	must I have been fibbing?
must you have been fibbing?
must she have been fibbing?
must we have been fibbing?
must you have been fibbing?
must they have been fibbing? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
mustn't I fib?
mustn't you fib?
mustn't she fib?
mustn't we fib?
mustn't you fib?
mustn't they fib? 	mustn't I be fibbing?
mustn't you be fibbing?
mustn't she be fibbing?
mustn't we be fibbing?
mustn't you be fibbing?
mustn't they be fibbing? 	mustn't I have fibbed?
mustn't you have fibbed?
mustn't she have fibbed?
mustn't we have fibbed?
mustn't you have fibbed?
mustn't they have fibbed? 	mustn't I have been fibbing?
mustn't you have been fibbing?
mustn't she have been fibbing?
mustn't we have been fibbing?
mustn't you have been fibbing?
mustn't they have been fibbing?