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 couldn't help you couldn't help he couldn't help we couldn't help you couldn't help they couldn't help
V-ing form
I couldn't be helping you couldn't be helping he couldn't be helping we couldn't be helping you couldn't be helping they couldn't be helping
Perfect
I couldn't have helped you couldn't have helped he couldn't have helped we couldn't have helped you couldn't have helped they couldn't have helped
V-ing perfect
I couldn't have been helping you couldn't have been helping he couldn't have been helping we couldn't have been helping you couldn't have been helping they couldn't 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
couldn't I help? couldn't you help? couldn't he help? couldn't we help? couldn't you help? couldn't they help?
V-ing form
couldn't I be helping? couldn't you be helping? couldn't he be helping? couldn't we be helping? couldn't you be helping? couldn't they be helping?
Perfect
couldn't I have helped? couldn't you have helped? couldn't he have helped? couldn't we have helped? couldn't you have helped? couldn't they have helped?
V-ing perfect
couldn't I have been helping? couldn't you have been helping? couldn't he have been helping? couldn't we have been helping? couldn't you have been helping? couldn't they have been helping?