must muck
Regular verb: muck - mucked- mucked

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I must muck
you must muck
he must muck
we must muck
you must muck
they must muck 	I must be mucking
you must be mucking
he must be mucking
we must be mucking
you must be mucking
they must be mucking	I must have mucked
you must have mucked
he must have mucked
we must have mucked
you must have mucked
they must have mucked	I must have been mucking
you must have been mucking
he must have been mucking
we must have been mucking
you must have been mucking
they must have been mucking	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I mustn't muck
you mustn't muck
he mustn't muck
we mustn't muck
you mustn't muck
they mustn't muck 	I mustn't be mucking
you mustn't be mucking
he mustn't be mucking
we mustn't be mucking
you mustn't be mucking
they mustn't be mucking	I mustn't have mucked
you mustn't have mucked
he mustn't have mucked
we mustn't have mucked
you mustn't have mucked
they mustn't have mucked	I mustn't have been mucking
you mustn't have been mucking
he mustn't have been mucking
we mustn't have been mucking
you mustn't have been mucking
they mustn't have been mucking	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
must I muck?
must you muck?
must he muck?
must we muck?
must you muck?
must they muck? 	must I be mucking?
must you be mucking?
must he be mucking?
must we be mucking?
must you be mucking?
must they be mucking? 	must I have mucked?
must you have mucked?
must he have mucked?
must we have mucked?
must you have mucked?
must they have mucked? 	must I have been mucking?
must you have been mucking?
must he have been mucking?
must we have been mucking?
must you have been mucking?
must they have been mucking? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
mustn't I muck?
mustn't you muck?
mustn't he muck?
mustn't we muck?
mustn't you muck?
mustn't they muck? 	mustn't I be mucking?
mustn't you be mucking?
mustn't he be mucking?
mustn't we be mucking?
mustn't you be mucking?
mustn't they be mucking? 	mustn't I have mucked?
mustn't you have mucked?
mustn't he have mucked?
mustn't we have mucked?
mustn't you have mucked?
mustn't they have mucked? 	mustn't I have been mucking?
mustn't you have been mucking?
mustn't he have been mucking?
mustn't we have been mucking?
mustn't you have been mucking?
mustn't they have been mucking?