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