I could assert you could assert he could assert we could assert you could assert they could assert
V-ing form
I could be asserting you could be asserting he could be asserting we could be asserting you could be asserting they could be asserting
Perfect
I could have asserted you could have asserted he could have asserted we could have asserted you could have asserted they could have asserted
V-ing perfect
I could have been asserting you could have been asserting he could have been asserting we could have been asserting you could have been asserting they could have been asserting
Negation
Simple form
I could not assert you could not assert he could not assert we could not assert you could not assert they could not assert
V-ing form
I could not be asserting you could not be asserting he could not be asserting we could not be asserting you could not be asserting they could not be asserting
Perfect
I could not have asserted you could not have asserted he could not have asserted we could not have asserted you could not have asserted they could not have asserted
V-ing perfect
I could not have been asserting you could not have been asserting he could not have been asserting we could not have been asserting you could not have been asserting they could not have been asserting
Interrogative form
Simple form
could I assert? could you assert? could he assert? could we assert? could you assert? could they assert?
V-ing form
could I be asserting? could you be asserting? could he be asserting? could we be asserting? could you be asserting? could they be asserting?
Perfect
could I have asserted? could you have asserted? could he have asserted? could we have asserted? could you have asserted? could they have asserted?
V-ing perfect
could I have been asserting? could you have been asserting? could he have been asserting? could we have been asserting? could you have been asserting? could they have been asserting?
Interro-negative form
Simple form
could I not assert? could you not assert? could he not assert? could we not assert? could you not assert? could they not assert?
V-ing form
could I not be asserting? could you not be asserting? could he not be asserting? could we not be asserting? could you not be asserting? could they not be asserting?
Perfect
could I not have asserted? could you not have asserted? could he not have asserted? could we not have asserted? could you not have asserted? could they not have asserted?
V-ing perfect
could I not have been asserting? could you not have been asserting? could he not have been asserting? could we not have been asserting? could you not have been asserting? could they not have been asserting?