I could help you could help he could help we could help you could help they could help
V-ing form
I could be helping you could be helping he could be helping we could be helping you could be helping they could be helping
Perfect
I could have helped you could have helped he could have helped we could have helped you could have helped they could have helped
V-ing perfect
I could have been helping you could have been helping he could have been helping we could have been helping you could have been helping they could have been helping
Negation
Simple form
I could not help you could not help he could not help we could not help you could not help they could not help
V-ing form
I could not be helping you could not be helping he could not be helping we could not be helping you could not be helping they could not be helping
Perfect
I could not have helped you could not have helped he could not have helped we could not have helped you could not have helped they could not have helped
V-ing perfect
I could not have been helping you could not have been helping he could not have been helping we could not have been helping you could not have been helping they could not have been helping
Interrogative form
Simple form
could I help? could you help? could he help? could we help? could you help? could they help?
V-ing form
could I be helping? could you be helping? could he be helping? could we be helping? could you be helping? could they be helping?
Perfect
could I have helped? could you have helped? could he have helped? could we have helped? could you have helped? could they have helped?
V-ing perfect
could I have been helping? could you have been helping? could he have been helping? could we have been helping? could you have been helping? could they have been helping?
Interro-negative form
Simple form
could I not help? could you not help? could he not help? could we not help? could you not help? could they not help?
V-ing form
could I not be helping? could you not be helping? could he not be helping? could we not be helping? could you not be helping? could they not be helping?
Perfect
could I not have helped? could you not have helped? could he not have helped? could we not have helped? could you not have helped? could they not have helped?
V-ing perfect
could I not have been helping? could you not have been helping? could he not have been helping? could we not have been helping? could you not have been helping? could they not have been helping?