I could chew you could chew he could chew we could chew you could chew they could chew
V-ing form
I could be chewing you could be chewing he could be chewing we could be chewing you could be chewing they could be chewing
Perfect
I could have chewed you could have chewed he could have chewed we could have chewed you could have chewed they could have chewed
V-ing perfect
I could have been chewing you could have been chewing he could have been chewing we could have been chewing you could have been chewing they could have been chewing
Negation
Simple form
I couldn't chew you couldn't chew he couldn't chew we couldn't chew you couldn't chew they couldn't chew
V-ing form
I couldn't be chewing you couldn't be chewing he couldn't be chewing we couldn't be chewing you couldn't be chewing they couldn't be chewing
Perfect
I couldn't have chewed you couldn't have chewed he couldn't have chewed we couldn't have chewed you couldn't have chewed they couldn't have chewed
V-ing perfect
I couldn't have been chewing you couldn't have been chewing he couldn't have been chewing we couldn't have been chewing you couldn't have been chewing they couldn't have been chewing
Interrogative form
Simple form
could I chew? could you chew? could he chew? could we chew? could you chew? could they chew?
V-ing form
could I be chewing? could you be chewing? could he be chewing? could we be chewing? could you be chewing? could they be chewing?
Perfect
could I have chewed? could you have chewed? could he have chewed? could we have chewed? could you have chewed? could they have chewed?
V-ing perfect
could I have been chewing? could you have been chewing? could he have been chewing? could we have been chewing? could you have been chewing? could they have been chewing?
Interro-negative form
Simple form
couldn't I chew? couldn't you chew? couldn't he chew? couldn't we chew? couldn't you chew? couldn't they chew?
V-ing form
couldn't I be chewing? couldn't you be chewing? couldn't he be chewing? couldn't we be chewing? couldn't you be chewing? couldn't they be chewing?
Perfect
couldn't I have chewed? couldn't you have chewed? couldn't he have chewed? couldn't we have chewed? couldn't you have chewed? couldn't they have chewed?
V-ing perfect
couldn't I have been chewing? couldn't you have been chewing? couldn't he have been chewing? couldn't we have been chewing? couldn't you have been chewing? couldn't they have been chewing?