must croak
Regular verb: croak - croaked- croaked

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I must croak
you must croak
she must croak
we must croak
you must croak
they must croak 	I must be croaking
you must be croaking
she must be croaking
we must be croaking
you must be croaking
they must be croaking	I must have croaked
you must have croaked
she must have croaked
we must have croaked
you must have croaked
they must have croaked	I must have been croaking
you must have been croaking
she must have been croaking
we must have been croaking
you must have been croaking
they must have been croaking	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I mustn't croak
you mustn't croak
she mustn't croak
we mustn't croak
you mustn't croak
they mustn't croak 	I mustn't be croaking
you mustn't be croaking
she mustn't be croaking
we mustn't be croaking
you mustn't be croaking
they mustn't be croaking	I mustn't have croaked
you mustn't have croaked
she mustn't have croaked
we mustn't have croaked
you mustn't have croaked
they mustn't have croaked	I mustn't have been croaking
you mustn't have been croaking
she mustn't have been croaking
we mustn't have been croaking
you mustn't have been croaking
they mustn't have been croaking	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
must I croak?
must you croak?
must she croak?
must we croak?
must you croak?
must they croak? 	must I be croaking?
must you be croaking?
must she be croaking?
must we be croaking?
must you be croaking?
must they be croaking? 	must I have croaked?
must you have croaked?
must she have croaked?
must we have croaked?
must you have croaked?
must they have croaked? 	must I have been croaking?
must you have been croaking?
must she have been croaking?
must we have been croaking?
must you have been croaking?
must they have been croaking? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
mustn't I croak?
mustn't you croak?
mustn't she croak?
mustn't we croak?
mustn't you croak?
mustn't they croak? 	mustn't I be croaking?
mustn't you be croaking?
mustn't she be croaking?
mustn't we be croaking?
mustn't you be croaking?
mustn't they be croaking? 	mustn't I have croaked?
mustn't you have croaked?
mustn't she have croaked?
mustn't we have croaked?
mustn't you have croaked?
mustn't they have croaked? 	mustn't I have been croaking?
mustn't you have been croaking?
mustn't she have been croaking?
mustn't we have been croaking?
mustn't you have been croaking?
mustn't they have been croaking?