I could operate you could operate she could operate we could operate you could operate they could operate
V-ing form
I could be operating you could be operating she could be operating we could be operating you could be operating they could be operating
Perfect
I could have operated you could have operated she 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 she 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 she 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 she 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 she 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 she 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 she operate? could we operate? could you operate? could they operate?
V-ing form
could I be operating? could you be operating? could she be operating? could we be operating? could you be operating? could they be operating?
Perfect
could I have operated? could you have operated? could she 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 she 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 she 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 she 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 she 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 she not have been operating? could we not have been operating? could you not have been operating? could they not have been operating?