I could diagram you could diagram he could diagram we could diagram you could diagram they could diagram
V-ing form
I could be diagraming you could be diagraming he could be diagraming we could be diagraming you could be diagraming they could be diagraming
Perfect
I could have diagramed you could have diagramed he could have diagramed we could have diagramed you could have diagramed they could have diagramed
V-ing perfect
I could have been diagraming you could have been diagraming he could have been diagraming we could have been diagraming you could have been diagraming they could have been diagraming
Negation
Simple form
I could not diagram you could not diagram he could not diagram we could not diagram you could not diagram they could not diagram
V-ing form
I could not be diagraming you could not be diagraming he could not be diagraming we could not be diagraming you could not be diagraming they could not be diagraming
Perfect
I could not have diagramed you could not have diagramed he could not have diagramed we could not have diagramed you could not have diagramed they could not have diagramed
V-ing perfect
I could not have been diagraming you could not have been diagraming he could not have been diagraming we could not have been diagraming you could not have been diagraming they could not have been diagraming
Interrogative form
Simple form
could I diagram? could you diagram? could he diagram? could we diagram? could you diagram? could they diagram?
V-ing form
could I be diagraming? could you be diagraming? could he be diagraming? could we be diagraming? could you be diagraming? could they be diagraming?
Perfect
could I have diagramed? could you have diagramed? could he have diagramed? could we have diagramed? could you have diagramed? could they have diagramed?
V-ing perfect
could I have been diagraming? could you have been diagraming? could he have been diagraming? could we have been diagraming? could you have been diagraming? could they have been diagraming?
Interro-negative form
Simple form
could I not diagram? could you not diagram? could he not diagram? could we not diagram? could you not diagram? could they not diagram?
V-ing form
could I not be diagraming? could you not be diagraming? could he not be diagraming? could we not be diagraming? could you not be diagraming? could they not be diagraming?
Perfect
could I not have diagramed? could you not have diagramed? could he not have diagramed? could we not have diagramed? could you not have diagramed? could they not have diagramed?
V-ing perfect
could I not have been diagraming? could you not have been diagraming? could he not have been diagraming? could we not have been diagraming? could you not have been diagraming? could they not have been diagraming?