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