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