I could flag you could flag he could flag we could flag you could flag they could flag
V-ing form
I could be flagging you could be flagging he could be flagging we could be flagging you could be flagging they could be flagging
Perfect
I could have flagged you could have flagged he could have flagged we could have flagged you could have flagged they could have flagged
V-ing perfect
I could have been flagging you could have been flagging he could have been flagging we could have been flagging you could have been flagging they could have been flagging
Negation
Simple form
I could not flag you could not flag he could not flag we could not flag you could not flag they could not flag
V-ing form
I could not be flagging you could not be flagging he could not be flagging we could not be flagging you could not be flagging they could not be flagging
Perfect
I could not have flagged you could not have flagged he could not have flagged we could not have flagged you could not have flagged they could not have flagged
V-ing perfect
I could not have been flagging you could not have been flagging he could not have been flagging we could not have been flagging you could not have been flagging they could not have been flagging
Interrogative form
Simple form
could I flag? could you flag? could he flag? could we flag? could you flag? could they flag?
V-ing form
could I be flagging? could you be flagging? could he be flagging? could we be flagging? could you be flagging? could they be flagging?
Perfect
could I have flagged? could you have flagged? could he have flagged? could we have flagged? could you have flagged? could they have flagged?
V-ing perfect
could I have been flagging? could you have been flagging? could he have been flagging? could we have been flagging? could you have been flagging? could they have been flagging?
Interro-negative form
Simple form
could I not flag? could you not flag? could he not flag? could we not flag? could you not flag? could they not flag?
V-ing form
could I not be flagging? could you not be flagging? could he not be flagging? could we not be flagging? could you not be flagging? could they not be flagging?
Perfect
could I not have flagged? could you not have flagged? could he not have flagged? could we not have flagged? could you not have flagged? could they not have flagged?
V-ing perfect
could I not have been flagging? could you not have been flagging? could he not have been flagging? could we not have been flagging? could you not have been flagging? could they not have been flagging?