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