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