English verb conjugation
CAN QUACK

Regular verb: quack - quacked - quacked

Affirmation

Simple form	V-ing form
I can quack you can quack he can quack we can quack you can quack they can quack	I can be quacking you can be quacking he can be quacking we can be quacking you can be quacking they can be quacking
Perfect	V-ing perfect
I can have quacked you can have quacked he can have quacked we can have quacked you can have quacked they can have quacked	I can have been quacking you can have been quacking he can have been quacking we can have been quacking you can have been quacking they can have been quacking

Negation

Simple form	V-ing form
I cannot quack you cannot quack he cannot quack we cannot quack you cannot quack they cannot quack	I cannot be quacking you cannot be quacking he cannot be quacking we cannot be quacking you cannot be quacking they cannot be quacking
Perfect	V-ing perfect
I cannot have quacked you cannot have quacked he cannot have quacked we cannot have quacked you cannot have quacked they cannot have quacked	I cannot have been quacking you cannot have been quacking he cannot have been quacking we cannot have been quacking you cannot have been quacking they cannot have been quacking

Interrogative form

Simple form	V-ing form
can I quack? can you quack? can he quack? can we quack? can you quack? can they quack?	can I be quacking? can you be quacking? can he be quacking? can we be quacking? can you be quacking? can they be quacking?
Perfect	V-ing perfect
can I have quacked? can you have quacked? can he have quacked? can we have quacked? can you have quacked? can they have quacked?	can I have been quacking? can you have been quacking? can he have been quacking? can we have been quacking? can you have been quacking? can they have been quacking?

Interro-negative form

Simple form	V-ing form
can I not quack? can you not quack? can he not quack? can we not quack? can you not quack? can they not quack?	can I not be quacking? can you not be quacking? can he not be quacking? can we not be quacking? can you not be quacking? can they not be quacking?
Perfect	V-ing perfect
can I not have quacked? can you not have quacked? can he not have quacked? can we not have quacked? can you not have quacked? can they not have quacked?	can I not have been quacking? can you not have been quacking? can he not have been quacking? can we not have been quacking? can you not have been quacking? can they not have been quacking?