I could dupe you could dupe she could dupe we could dupe you could dupe they could dupe
V-ing form
I could be duping you could be duping she could be duping we could be duping you could be duping they could be duping
Perfect
I could have duped you could have duped she could have duped we could have duped you could have duped they could have duped
V-ing perfect
I could have been duping you could have been duping she could have been duping we could have been duping you could have been duping they could have been duping
Negation
Simple form
I couldn't dupe you couldn't dupe she couldn't dupe we couldn't dupe you couldn't dupe they couldn't dupe
V-ing form
I couldn't be duping you couldn't be duping she couldn't be duping we couldn't be duping you couldn't be duping they couldn't be duping
Perfect
I couldn't have duped you couldn't have duped she couldn't have duped we couldn't have duped you couldn't have duped they couldn't have duped
V-ing perfect
I couldn't have been duping you couldn't have been duping she couldn't have been duping we couldn't have been duping you couldn't have been duping they couldn't have been duping
Interrogative form
Simple form
could I dupe? could you dupe? could she dupe? could we dupe? could you dupe? could they dupe?
V-ing form
could I be duping? could you be duping? could she be duping? could we be duping? could you be duping? could they be duping?
Perfect
could I have duped? could you have duped? could she have duped? could we have duped? could you have duped? could they have duped?
V-ing perfect
could I have been duping? could you have been duping? could she have been duping? could we have been duping? could you have been duping? could they have been duping?
Interro-negative form
Simple form
couldn't I dupe? couldn't you dupe? couldn't she dupe? couldn't we dupe? couldn't you dupe? couldn't they dupe?
V-ing form
couldn't I be duping? couldn't you be duping? couldn't she be duping? couldn't we be duping? couldn't you be duping? couldn't they be duping?
Perfect
couldn't I have duped? couldn't you have duped? couldn't she have duped? couldn't we have duped? couldn't you have duped? couldn't they have duped?
V-ing perfect
couldn't I have been duping? couldn't you have been duping? couldn't she have been duping? couldn't we have been duping? couldn't you have been duping? couldn't they have been duping?