English verb conjugation
COULD YACK

Regular verb: yack - yacked - yacked

Affirmation

Simple form	V-ing form
I could yack you could yack he could yack we could yack you could yack they could yack	I could be yacking you could be yacking he could be yacking we could be yacking you could be yacking they could be yacking
Perfect	V-ing perfect
I could have yacked you could have yacked he could have yacked we could have yacked you could have yacked they could have yacked	I could have been yacking you could have been yacking he could have been yacking we could have been yacking you could have been yacking they could have been yacking

Negation

Simple form	V-ing form
I couldn't yack you couldn't yack he couldn't yack we couldn't yack you couldn't yack they couldn't yack	I couldn't be yacking you couldn't be yacking he couldn't be yacking we couldn't be yacking you couldn't be yacking they couldn't be yacking
Perfect	V-ing perfect
I couldn't have yacked you couldn't have yacked he couldn't have yacked we couldn't have yacked you couldn't have yacked they couldn't have yacked	I couldn't have been yacking you couldn't have been yacking he couldn't have been yacking we couldn't have been yacking you couldn't have been yacking they couldn't have been yacking

Interrogative form

Simple form	V-ing form
could I yack? could you yack? could he yack? could we yack? could you yack? could they yack?	could I be yacking? could you be yacking? could he be yacking? could we be yacking? could you be yacking? could they be yacking?
Perfect	V-ing perfect
could I have yacked? could you have yacked? could he have yacked? could we have yacked? could you have yacked? could they have yacked?	could I have been yacking? could you have been yacking? could he have been yacking? could we have been yacking? could you have been yacking? could they have been yacking?

Interro-negative form

Simple form	V-ing form
couldn't I yack? couldn't you yack? couldn't he yack? couldn't we yack? couldn't you yack? couldn't they yack?	couldn't I be yacking? couldn't you be yacking? couldn't he be yacking? couldn't we be yacking? couldn't you be yacking? couldn't they be yacking?
Perfect	V-ing perfect
couldn't I have yacked? couldn't you have yacked? couldn't he have yacked? couldn't we have yacked? couldn't you have yacked? couldn't they have yacked?	couldn't I have been yacking? couldn't you have been yacking? couldn't he have been yacking? couldn't we have been yacking? couldn't you have been yacking? couldn't they have been yacking?