English verb conjugation
CAN STACK

Regular verb: stack - stacked - stacked

Affirmation

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

Negation

Simple form	V-ing form
I can't stack you can't stack he can't stack we can't stack you can't stack they can't stack	I can't be stacking you can't be stacking he can't be stacking we can't be stacking you can't be stacking they can't be stacking
Perfect	V-ing perfect
I can't have stacked you can't have stacked he can't have stacked we can't have stacked you can't have stacked they can't have stacked	I can't have been stacking you can't have been stacking he can't have been stacking we can't have been stacking you can't have been stacking they can't have been stacking

Interrogative form

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

Interro-negative form

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