I could open you could open she could open we could open you could open they could open
V-ing form
I could be opening you could be opening she could be opening we could be opening you could be opening they could be opening
Perfect
I could have opened you could have opened she could have opened we could have opened you could have opened they could have opened
V-ing perfect
I could have been opening you could have been opening she could have been opening we could have been opening you could have been opening they could have been opening
Negation
Simple form
I could not open you could not open she could not open we could not open you could not open they could not open
V-ing form
I could not be opening you could not be opening she could not be opening we could not be opening you could not be opening they could not be opening
Perfect
I could not have opened you could not have opened she could not have opened we could not have opened you could not have opened they could not have opened
V-ing perfect
I could not have been opening you could not have been opening she could not have been opening we could not have been opening you could not have been opening they could not have been opening
Interrogative form
Simple form
could I open? could you open? could she open? could we open? could you open? could they open?
V-ing form
could I be opening? could you be opening? could she be opening? could we be opening? could you be opening? could they be opening?
Perfect
could I have opened? could you have opened? could she have opened? could we have opened? could you have opened? could they have opened?
V-ing perfect
could I have been opening? could you have been opening? could she have been opening? could we have been opening? could you have been opening? could they have been opening?
Interro-negative form
Simple form
could I not open? could you not open? could she not open? could we not open? could you not open? could they not open?
V-ing form
could I not be opening? could you not be opening? could she not be opening? could we not be opening? could you not be opening? could they not be opening?
Perfect
could I not have opened? could you not have opened? could she not have opened? could we not have opened? could you not have opened? could they not have opened?
V-ing perfect
could I not have been opening? could you not have been opening? could she not have been opening? could we not have been opening? could you not have been opening? could they not have been opening?