I could rivet you could rivet she could rivet we could rivet you could rivet they could rivet
V-ing form
I could be riveting you could be riveting she could be riveting we could be riveting you could be riveting they could be riveting
Perfect
I could have riveted you could have riveted she 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 she 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 she 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 she 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 she 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 she 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 she rivet? could we rivet? could you rivet? could they rivet?
V-ing form
could I be riveting? could you be riveting? could she be riveting? could we be riveting? could you be riveting? could they be riveting?
Perfect
could I have riveted? could you have riveted? could she 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 she 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 she 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 she 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 she 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 she have been riveting? couldn't we have been riveting? couldn't you have been riveting? couldn't they have been riveting?