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