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