I could operate you could operate he could operate we could operate you could operate they could operate
V-ing form
I could be operating you could be operating he could be operating we could be operating you could be operating they could be operating
Perfect
I could have operated you could have operated he could have operated we could have operated you could have operated they could have operated
V-ing perfect
I could have been operating you could have been operating he could have been operating we could have been operating you could have been operating they could have been operating
Negation
Simple form
I could not operate you could not operate he could not operate we could not operate you could not operate they could not operate
V-ing form
I could not be operating you could not be operating he could not be operating we could not be operating you could not be operating they could not be operating
Perfect
I could not have operated you could not have operated he could not have operated we could not have operated you could not have operated they could not have operated
V-ing perfect
I could not have been operating you could not have been operating he could not have been operating we could not have been operating you could not have been operating they could not have been operating
Interrogative form
Simple form
could I operate? could you operate? could he operate? could we operate? could you operate? could they operate?
V-ing form
could I be operating? could you be operating? could he be operating? could we be operating? could you be operating? could they be operating?
Perfect
could I have operated? could you have operated? could he have operated? could we have operated? could you have operated? could they have operated?
V-ing perfect
could I have been operating? could you have been operating? could he have been operating? could we have been operating? could you have been operating? could they have been operating?
Interro-negative form
Simple form
could I not operate? could you not operate? could he not operate? could we not operate? could you not operate? could they not operate?
V-ing form
could I not be operating? could you not be operating? could he not be operating? could we not be operating? could you not be operating? could they not be operating?
Perfect
could I not have operated? could you not have operated? could he not have operated? could we not have operated? could you not have operated? could they not have operated?
V-ing perfect
could I not have been operating? could you not have been operating? could he not have been operating? could we not have been operating? could you not have been operating? could they not have been operating?