I could preface you could preface she could preface we could preface you could preface they could preface
V-ing form
I could be prefacing you could be prefacing she could be prefacing we could be prefacing you could be prefacing they could be prefacing
Perfect
I could have prefaced you could have prefaced she could have prefaced we could have prefaced you could have prefaced they could have prefaced
V-ing perfect
I could have been prefacing you could have been prefacing she could have been prefacing we could have been prefacing you could have been prefacing they could have been prefacing
Negation
Simple form
I couldn't preface you couldn't preface she couldn't preface we couldn't preface you couldn't preface they couldn't preface
V-ing form
I couldn't be prefacing you couldn't be prefacing she couldn't be prefacing we couldn't be prefacing you couldn't be prefacing they couldn't be prefacing
Perfect
I couldn't have prefaced you couldn't have prefaced she couldn't have prefaced we couldn't have prefaced you couldn't have prefaced they couldn't have prefaced
V-ing perfect
I couldn't have been prefacing you couldn't have been prefacing she couldn't have been prefacing we couldn't have been prefacing you couldn't have been prefacing they couldn't have been prefacing
Interrogative form
Simple form
could I preface? could you preface? could she preface? could we preface? could you preface? could they preface?
V-ing form
could I be prefacing? could you be prefacing? could she be prefacing? could we be prefacing? could you be prefacing? could they be prefacing?
Perfect
could I have prefaced? could you have prefaced? could she have prefaced? could we have prefaced? could you have prefaced? could they have prefaced?
V-ing perfect
could I have been prefacing? could you have been prefacing? could she have been prefacing? could we have been prefacing? could you have been prefacing? could they have been prefacing?
Interro-negative form
Simple form
couldn't I preface? couldn't you preface? couldn't she preface? couldn't we preface? couldn't you preface? couldn't they preface?
V-ing form
couldn't I be prefacing? couldn't you be prefacing? couldn't she be prefacing? couldn't we be prefacing? couldn't you be prefacing? couldn't they be prefacing?
Perfect
couldn't I have prefaced? couldn't you have prefaced? couldn't she have prefaced? couldn't we have prefaced? couldn't you have prefaced? couldn't they have prefaced?
V-ing perfect
couldn't I have been prefacing? couldn't you have been prefacing? couldn't she have been prefacing? couldn't we have been prefacing? couldn't you have been prefacing? couldn't they have been prefacing?