English verb conjugation
COULD QUACK

Regular verb: quack - quacked - quacked

Affirmation

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

Negation

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

Interrogative form

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

Interro-negative form

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