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