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