English verb conjugation
MUST STACK

Regular verb: stack - stacked - stacked

Affirmation

Simple form	V-ing form
I must stack you must stack he must stack we must stack you must stack they must stack	I must be stacking you must be stacking he must be stacking we must be stacking you must be stacking they must be stacking
Perfect	V-ing perfect
I must have stacked you must have stacked he must have stacked we must have stacked you must have stacked they must have stacked	I must have been stacking you must have been stacking he must have been stacking we must have been stacking you must have been stacking they must have been stacking

Negation

Simple form	V-ing form
I must not stack you must not stack he must not stack we must not stack you must not stack they must not stack	I must not be stacking you must not be stacking he must not be stacking we must not be stacking you must not be stacking they must not be stacking
Perfect	V-ing perfect
I must not have stacked you must not have stacked he must not have stacked we must not have stacked you must not have stacked they must not have stacked	I must not have been stacking you must not have been stacking he must not have been stacking we must not have been stacking you must not have been stacking they must not have been stacking

Interrogative form

Simple form	V-ing form
must I stack? must you stack? must he stack? must we stack? must you stack? must they stack?	must I be stacking? must you be stacking? must he be stacking? must we be stacking? must you be stacking? must they be stacking?
Perfect	V-ing perfect
must I have stacked? must you have stacked? must he have stacked? must we have stacked? must you have stacked? must they have stacked?	must I have been stacking? must you have been stacking? must he have been stacking? must we have been stacking? must you have been stacking? must they have been stacking?

Interro-negative form

Simple form	V-ing form
must I not stack? must you not stack? must he not stack? must we not stack? must you not stack? must they not stack?	must I not be stacking? must you not be stacking? must he not be stacking? must we not be stacking? must you not be stacking? must they not be stacking?
Perfect	V-ing perfect
must I not have stacked? must you not have stacked? must he not have stacked? must we not have stacked? must you not have stacked? must they not have stacked?	must I not have been stacking? must you not have been stacking? must he not have been stacking? must we not have been stacking? must you not have been stacking? must they not have been stacking?