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