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 could not fold you could not fold he could not fold we could not fold you could not fold they could not fold
V-ing form
I could not be folding you could not be folding he could not be folding we could not be folding you could not be folding they could not be folding
Perfect
I could not have folded you could not have folded he could not have folded we could not have folded you could not have folded they could not have folded
V-ing perfect
I could not have been folding you could not have been folding he could not have been folding we could not have been folding you could not have been folding they could not 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
could I not fold? could you not fold? could he not fold? could we not fold? could you not fold? could they not fold?
V-ing form
could I not be folding? could you not be folding? could he not be folding? could we not be folding? could you not be folding? could they not be folding?
Perfect
could I not have folded? could you not have folded? could he not have folded? could we not have folded? could you not have folded? could they not have folded?
V-ing perfect
could I not have been folding? could you not have been folding? could he not have been folding? could we not have been folding? could you not have been folding? could they not have been folding?