must quack
Regular verb: quack - quacked- quacked

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I must quack
you must quack
he must quack
we must quack
you must quack
they must quack 	I must be quacking
you must be quacking
he must be quacking
we must be quacking
you must be quacking
they must be quacking	I must have quacked
you must have quacked
he 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
he 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 must not quack
you must not quack
he must not quack
we must not quack
you must not quack
they must not quack 	I must not be quacking
you must not be quacking
he must not be quacking
we must not be quacking
you must not be quacking
they must not be quacking	I must not have quacked
you must not have quacked
he must not have quacked
we must not have quacked
you must not have quacked
they must not have quacked	I must not have been quacking
you must not have been quacking
he must not have been quacking
we must not have been quacking
you must not have been quacking
they must not have been quacking	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
must I quack?
must you quack?
must he quack?
must we quack?
must you quack?
must they quack? 	must I be quacking?
must you be quacking?
must he be quacking?
must we be quacking?
must you be quacking?
must they be quacking? 	must I have quacked?
must you have quacked?
must he 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 he 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 	
must I not quack?
must you not quack?
must he not quack?
must we not quack?
must you not quack?
must they not quack? 	must I not be quacking?
must you not be quacking?
must he not be quacking?
must we not be quacking?
must you not be quacking?
must they not be quacking? 	must I not have quacked?
must you not have quacked?
must he not have quacked?
must we not have quacked?
must you not have quacked?
must they not have quacked? 	must I not have been quacking?
must you not have been quacking?
must he not have been quacking?
must we not have been quacking?
must you not have been quacking?
must they not have been quacking?