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 mustn't stack you mustn't stack he mustn't stack we mustn't stack you mustn't stack they mustn't stack	I mustn't be stacking you mustn't be stacking he mustn't be stacking we mustn't be stacking you mustn't be stacking they mustn't be stacking
Perfect	V-ing perfect
I mustn't have stacked you mustn't have stacked he mustn't have stacked we mustn't have stacked you mustn't have stacked they mustn't have stacked	I mustn't have been stacking you mustn't have been stacking he mustn't have been stacking we mustn't have been stacking you mustn't have been stacking they mustn't 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
mustn't I stack? mustn't you stack? mustn't he stack? mustn't we stack? mustn't you stack? mustn't they stack?	mustn't I be stacking? mustn't you be stacking? mustn't he be stacking? mustn't we be stacking? mustn't you be stacking? mustn't they be stacking?
Perfect	V-ing perfect
mustn't I have stacked? mustn't you have stacked? mustn't he have stacked? mustn't we have stacked? mustn't you have stacked? mustn't they have stacked?	mustn't I have been stacking? mustn't you have been stacking? mustn't he have been stacking? mustn't we have been stacking? mustn't you have been stacking? mustn't they have been stacking?