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