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