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 could not fever you could not fever he could not fever we could not fever you could not fever they could not fever
V-ing form
I could not be fevering you could not be fevering he could not be fevering we could not be fevering you could not be fevering they could not be fevering
Perfect
I could not have fevered you could not have fevered he could not have fevered we could not have fevered you could not have fevered they could not have fevered
V-ing perfect
I could not have been fevering you could not have been fevering he could not have been fevering we could not have been fevering you could not have been fevering they could not 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
could I not fever? could you not fever? could he not fever? could we not fever? could you not fever? could they not fever?
V-ing form
could I not be fevering? could you not be fevering? could he not be fevering? could we not be fevering? could you not be fevering? could they not be fevering?
Perfect
could I not have fevered? could you not have fevered? could he not have fevered? could we not have fevered? could you not have fevered? could they not have fevered?
V-ing perfect
could I not have been fevering? could you not have been fevering? could he not have been fevering? could we not have been fevering? could you not have been fevering? could they not have been fevering?