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