English verb conjugation
CAN STACK

Regular verb: stack - stacked - stacked

Affirmation

Simple form	V-ing form
I can stack you can stack she can stack we can stack you can stack they can stack	I can be stacking you can be stacking she 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 she 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 she 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 cannot stack you cannot stack she cannot stack we cannot stack you cannot stack they cannot stack	I cannot be stacking you cannot be stacking she cannot be stacking we cannot be stacking you cannot be stacking they cannot be stacking
Perfect	V-ing perfect
I cannot have stacked you cannot have stacked she cannot have stacked we cannot have stacked you cannot have stacked they cannot have stacked	I cannot have been stacking you cannot have been stacking she cannot have been stacking we cannot have been stacking you cannot have been stacking they cannot have been stacking

Interrogative form

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