I could ring you could ring he could ring we could ring you could ring they could ring
V-ing form
I could be ringing you could be ringing he could be ringing we could be ringing you could be ringing they could be ringing
Perfect
I could have rung you could have rung he could have rung we could have rung you could have rung they could have rung
V-ing perfect
I could have been ringing you could have been ringing he could have been ringing we could have been ringing you could have been ringing they could have been ringing
Negation
Simple form
I could not ring you could not ring he could not ring we could not ring you could not ring they could not ring
V-ing form
I could not be ringing you could not be ringing he could not be ringing we could not be ringing you could not be ringing they could not be ringing
Perfect
I could not have rung you could not have rung he could not have rung we could not have rung you could not have rung they could not have rung
V-ing perfect
I could not have been ringing you could not have been ringing he could not have been ringing we could not have been ringing you could not have been ringing they could not have been ringing
Interrogative form
Simple form
could I ring? could you ring? could he ring? could we ring? could you ring? could they ring?
V-ing form
could I be ringing? could you be ringing? could he be ringing? could we be ringing? could you be ringing? could they be ringing?
Perfect
could I have rung? could you have rung? could he have rung? could we have rung? could you have rung? could they have rung?
V-ing perfect
could I have been ringing? could you have been ringing? could he have been ringing? could we have been ringing? could you have been ringing? could they have been ringing?
Interro-negative form
Simple form
could I not ring? could you not ring? could he not ring? could we not ring? could you not ring? could they not ring?
V-ing form
could I not be ringing? could you not be ringing? could he not be ringing? could we not be ringing? could you not be ringing? could they not be ringing?
Perfect
could I not have rung? could you not have rung? could he not have rung? could we not have rung? could you not have rung? could they not have rung?
V-ing perfect
could I not have been ringing? could you not have been ringing? could he not have been ringing? could we not have been ringing? could you not have been ringing? could they not have been ringing?