must quack
Regular verb: quack - quacked- quacked

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I must quack
you must quack
she must quack
we must quack
you must quack
they must quack 	I must be quacking
you must be quacking
she must be quacking
we must be quacking
you must be quacking
they must be quacking	I must have quacked
you must have quacked
she must have quacked
we must have quacked
you must have quacked
they must have quacked	I must have been quacking
you must have been quacking
she must have been quacking
we must have been quacking
you must have been quacking
they must have been quacking	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I mustn't quack
you mustn't quack
she mustn't quack
we mustn't quack
you mustn't quack
they mustn't quack 	I mustn't be quacking
you mustn't be quacking
she mustn't be quacking
we mustn't be quacking
you mustn't be quacking
they mustn't be quacking	I mustn't have quacked
you mustn't have quacked
she mustn't have quacked
we mustn't have quacked
you mustn't have quacked
they mustn't have quacked	I mustn't have been quacking
you mustn't have been quacking
she mustn't have been quacking
we mustn't have been quacking
you mustn't have been quacking
they mustn't have been quacking	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
must I quack?
must you quack?
must she quack?
must we quack?
must you quack?
must they quack? 	must I be quacking?
must you be quacking?
must she be quacking?
must we be quacking?
must you be quacking?
must they be quacking? 	must I have quacked?
must you have quacked?
must she have quacked?
must we have quacked?
must you have quacked?
must they have quacked? 	must I have been quacking?
must you have been quacking?
must she have been quacking?
must we have been quacking?
must you have been quacking?
must they have been quacking? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
mustn't I quack?
mustn't you quack?
mustn't she quack?
mustn't we quack?
mustn't you quack?
mustn't they quack? 	mustn't I be quacking?
mustn't you be quacking?
mustn't she be quacking?
mustn't we be quacking?
mustn't you be quacking?
mustn't they be quacking? 	mustn't I have quacked?
mustn't you have quacked?
mustn't she have quacked?
mustn't we have quacked?
mustn't you have quacked?
mustn't they have quacked? 	mustn't I have been quacking?
mustn't you have been quacking?
mustn't she have been quacking?
mustn't we have been quacking?
mustn't you have been quacking?
mustn't they have been quacking?