I could open you could open he could open we could open you could open they could open
V-ing form
I could be opening you could be opening he could be opening we could be opening you could be opening they could be opening
Perfect
I could have opened you could have opened he 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 he could have been opening we could have been opening you could have been opening they could have been opening
Negation
Simple form
I couldn't open you couldn't open he couldn't open we couldn't open you couldn't open they couldn't open
V-ing form
I couldn't be opening you couldn't be opening he couldn't be opening we couldn't be opening you couldn't be opening they couldn't be opening
Perfect
I couldn't have opened you couldn't have opened he couldn't have opened we couldn't have opened you couldn't have opened they couldn't have opened
V-ing perfect
I couldn't have been opening you couldn't have been opening he couldn't have been opening we couldn't have been opening you couldn't have been opening they couldn't have been opening
Interrogative form
Simple form
could I open? could you open? could he open? could we open? could you open? could they open?
V-ing form
could I be opening? could you be opening? could he be opening? could we be opening? could you be opening? could they be opening?
Perfect
could I have opened? could you have opened? could he 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 he have been opening? could we have been opening? could you have been opening? could they have been opening?
Interro-negative form
Simple form
couldn't I open? couldn't you open? couldn't he open? couldn't we open? couldn't you open? couldn't they open?
V-ing form
couldn't I be opening? couldn't you be opening? couldn't he be opening? couldn't we be opening? couldn't you be opening? couldn't they be opening?
Perfect
couldn't I have opened? couldn't you have opened? couldn't he have opened? couldn't we have opened? couldn't you have opened? couldn't they have opened?
V-ing perfect
couldn't I have been opening? couldn't you have been opening? couldn't he have been opening? couldn't we have been opening? couldn't you have been opening? couldn't they have been opening?