I could center you could center he could center we could center you could center they could center
V-ing form
I could be centering you could be centering he could be centering we could be centering you could be centering they could be centering
Perfect
I could have centered you could have centered he could have centered we could have centered you could have centered they could have centered
V-ing perfect
I could have been centering you could have been centering he could have been centering we could have been centering you could have been centering they could have been centering
Negation
Simple form
I could not center you could not center he could not center we could not center you could not center they could not center
V-ing form
I could not be centering you could not be centering he could not be centering we could not be centering you could not be centering they could not be centering
Perfect
I could not have centered you could not have centered he could not have centered we could not have centered you could not have centered they could not have centered
V-ing perfect
I could not have been centering you could not have been centering he could not have been centering we could not have been centering you could not have been centering they could not have been centering
Interrogative form
Simple form
could I center? could you center? could he center? could we center? could you center? could they center?
V-ing form
could I be centering? could you be centering? could he be centering? could we be centering? could you be centering? could they be centering?
Perfect
could I have centered? could you have centered? could he have centered? could we have centered? could you have centered? could they have centered?
V-ing perfect
could I have been centering? could you have been centering? could he have been centering? could we have been centering? could you have been centering? could they have been centering?
Interro-negative form
Simple form
could I not center? could you not center? could he not center? could we not center? could you not center? could they not center?
V-ing form
could I not be centering? could you not be centering? could he not be centering? could we not be centering? could you not be centering? could they not be centering?
Perfect
could I not have centered? could you not have centered? could he not have centered? could we not have centered? could you not have centered? could they not have centered?
V-ing perfect
could I not have been centering? could you not have been centering? could he not have been centering? could we not have been centering? could you not have been centering? could they not have been centering?