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 can't quack you can't quack he can't quack we can't quack you can't quack they can't quack	I can't be quacking you can't be quacking he can't be quacking we can't be quacking you can't be quacking they can't be quacking
Perfect	V-ing perfect
I can't have quacked you can't have quacked he can't have quacked we can't have quacked you can't have quacked they can't have quacked	I can't have been quacking you can't have been quacking he can't have been quacking we can't have been quacking you can't have been quacking they can't 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't I quack? can't you quack? can't he quack? can't we quack? can't you quack? can't they quack?	can't I be quacking? can't you be quacking? can't he be quacking? can't we be quacking? can't you be quacking? can't they be quacking?
Perfect	V-ing perfect
can't I have quacked? can't you have quacked? can't he have quacked? can't we have quacked? can't you have quacked? can't they have quacked?	can't I have been quacking? can't you have been quacking? can't he have been quacking? can't we have been quacking? can't you have been quacking? can't they have been quacking?