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