must stumble
Regular verb: stumble - stumbled- stumbled

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I must stumble
you must stumble
he must stumble
we must stumble
you must stumble
they must stumble 	I must be stumbling
you must be stumbling
he must be stumbling
we must be stumbling
you must be stumbling
they must be stumbling	I must have stumbled
you must have stumbled
he must have stumbled
we must have stumbled
you must have stumbled
they must have stumbled	I must have been stumbling
you must have been stumbling
he must have been stumbling
we must have been stumbling
you must have been stumbling
they must have been stumbling	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I mustn't stumble
you mustn't stumble
he mustn't stumble
we mustn't stumble
you mustn't stumble
they mustn't stumble 	I mustn't be stumbling
you mustn't be stumbling
he mustn't be stumbling
we mustn't be stumbling
you mustn't be stumbling
they mustn't be stumbling	I mustn't have stumbled
you mustn't have stumbled
he mustn't have stumbled
we mustn't have stumbled
you mustn't have stumbled
they mustn't have stumbled	I mustn't have been stumbling
you mustn't have been stumbling
he mustn't have been stumbling
we mustn't have been stumbling
you mustn't have been stumbling
they mustn't have been stumbling	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
must I stumble?
must you stumble?
must he stumble?
must we stumble?
must you stumble?
must they stumble? 	must I be stumbling?
must you be stumbling?
must he be stumbling?
must we be stumbling?
must you be stumbling?
must they be stumbling? 	must I have stumbled?
must you have stumbled?
must he have stumbled?
must we have stumbled?
must you have stumbled?
must they have stumbled? 	must I have been stumbling?
must you have been stumbling?
must he have been stumbling?
must we have been stumbling?
must you have been stumbling?
must they have been stumbling? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
mustn't I stumble?
mustn't you stumble?
mustn't he stumble?
mustn't we stumble?
mustn't you stumble?
mustn't they stumble? 	mustn't I be stumbling?
mustn't you be stumbling?
mustn't he be stumbling?
mustn't we be stumbling?
mustn't you be stumbling?
mustn't they be stumbling? 	mustn't I have stumbled?
mustn't you have stumbled?
mustn't he have stumbled?
mustn't we have stumbled?
mustn't you have stumbled?
mustn't they have stumbled? 	mustn't I have been stumbling?
mustn't you have been stumbling?
mustn't he have been stumbling?
mustn't we have been stumbling?
mustn't you have been stumbling?
mustn't they have been stumbling?