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