I could tire you could tire he could tire we could tire you could tire they could tire
V-ing form
I could be tiring you could be tiring he could be tiring we could be tiring you could be tiring they could be tiring
Perfect
I could have tired you could have tired he could have tired we could have tired you could have tired they could have tired
V-ing perfect
I could have been tiring you could have been tiring he could have been tiring we could have been tiring you could have been tiring they could have been tiring
Negation
Simple form
I could not tire you could not tire he could not tire we could not tire you could not tire they could not tire
V-ing form
I could not be tiring you could not be tiring he could not be tiring we could not be tiring you could not be tiring they could not be tiring
Perfect
I could not have tired you could not have tired he could not have tired we could not have tired you could not have tired they could not have tired
V-ing perfect
I could not have been tiring you could not have been tiring he could not have been tiring we could not have been tiring you could not have been tiring they could not have been tiring
Interrogative form
Simple form
could I tire? could you tire? could he tire? could we tire? could you tire? could they tire?
V-ing form
could I be tiring? could you be tiring? could he be tiring? could we be tiring? could you be tiring? could they be tiring?
Perfect
could I have tired? could you have tired? could he have tired? could we have tired? could you have tired? could they have tired?
V-ing perfect
could I have been tiring? could you have been tiring? could he have been tiring? could we have been tiring? could you have been tiring? could they have been tiring?
Interro-negative form
Simple form
could I not tire? could you not tire? could he not tire? could we not tire? could you not tire? could they not tire?
V-ing form
could I not be tiring? could you not be tiring? could he not be tiring? could we not be tiring? could you not be tiring? could they not be tiring?
Perfect
could I not have tired? could you not have tired? could he not have tired? could we not have tired? could you not have tired? could they not have tired?
V-ing perfect
could I not have been tiring? could you not have been tiring? could he not have been tiring? could we not have been tiring? could you not have been tiring? could they not have been tiring?