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