I could mar you could mar he could mar we could mar you could mar they could mar
V-ing form
I could be marring you could be marring he could be marring we could be marring you could be marring they could be marring
Perfect
I could have marred you could have marred he could have marred we could have marred you could have marred they could have marred
V-ing perfect
I could have been marring you could have been marring he could have been marring we could have been marring you could have been marring they could have been marring
Negation
Simple form
I could not mar you could not mar he could not mar we could not mar you could not mar they could not mar
V-ing form
I could not be marring you could not be marring he could not be marring we could not be marring you could not be marring they could not be marring
Perfect
I could not have marred you could not have marred he could not have marred we could not have marred you could not have marred they could not have marred
V-ing perfect
I could not have been marring you could not have been marring he could not have been marring we could not have been marring you could not have been marring they could not have been marring
Interrogative form
Simple form
could I mar? could you mar? could he mar? could we mar? could you mar? could they mar?
V-ing form
could I be marring? could you be marring? could he be marring? could we be marring? could you be marring? could they be marring?
Perfect
could I have marred? could you have marred? could he have marred? could we have marred? could you have marred? could they have marred?
V-ing perfect
could I have been marring? could you have been marring? could he have been marring? could we have been marring? could you have been marring? could they have been marring?
Interro-negative form
Simple form
could I not mar? could you not mar? could he not mar? could we not mar? could you not mar? could they not mar?
V-ing form
could I not be marring? could you not be marring? could he not be marring? could we not be marring? could you not be marring? could they not be marring?
Perfect
could I not have marred? could you not have marred? could he not have marred? could we not have marred? could you not have marred? could they not have marred?
V-ing perfect
could I not have been marring? could you not have been marring? could he not have been marring? could we not have been marring? could you not have been marring? could they not have been marring?