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