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