must muffle
Regular verb: muffle - muffled- muffled

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I must muffle
you must muffle
she must muffle
we must muffle
you must muffle
they must muffle 	I must be muffling
you must be muffling
she must be muffling
we must be muffling
you must be muffling
they must be muffling	I must have muffled
you must have muffled
she must have muffled
we must have muffled
you must have muffled
they must have muffled	I must have been muffling
you must have been muffling
she must have been muffling
we must have been muffling
you must have been muffling
they must have been muffling	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I must not muffle
you must not muffle
she must not muffle
we must not muffle
you must not muffle
they must not muffle 	I must not be muffling
you must not be muffling
she must not be muffling
we must not be muffling
you must not be muffling
they must not be muffling	I must not have muffled
you must not have muffled
she must not have muffled
we must not have muffled
you must not have muffled
they must not have muffled	I must not have been muffling
you must not have been muffling
she must not have been muffling
we must not have been muffling
you must not have been muffling
they must not have been muffling	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
must I muffle?
must you muffle?
must she muffle?
must we muffle?
must you muffle?
must they muffle? 	must I be muffling?
must you be muffling?
must she be muffling?
must we be muffling?
must you be muffling?
must they be muffling? 	must I have muffled?
must you have muffled?
must she have muffled?
must we have muffled?
must you have muffled?
must they have muffled? 	must I have been muffling?
must you have been muffling?
must she have been muffling?
must we have been muffling?
must you have been muffling?
must they have been muffling? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
must I not muffle?
must you not muffle?
must she not muffle?
must we not muffle?
must you not muffle?
must they not muffle? 	must I not be muffling?
must you not be muffling?
must she not be muffling?
must we not be muffling?
must you not be muffling?
must they not be muffling? 	must I not have muffled?
must you not have muffled?
must she not have muffled?
must we not have muffled?
must you not have muffled?
must they not have muffled? 	must I not have been muffling?
must you not have been muffling?
must she not have been muffling?
must we not have been muffling?
must you not have been muffling?
must they not have been muffling?