English verb conjugation
MUST QUACK

Regular verb: quack - quacked - quacked

Affirmation

Simple form	V-ing form
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
Perfect	V-ing perfect
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
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
Perfect	V-ing perfect
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
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?
Perfect	V-ing perfect
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
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?
Perfect	V-ing perfect
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?