I could commemorate you could commemorate he could commemorate we could commemorate you could commemorate they could commemorate
V-ing form
I could be commemorating you could be commemorating he could be commemorating we could be commemorating you could be commemorating they could be commemorating
Perfect
I could have commemorated you could have commemorated he could have commemorated we could have commemorated you could have commemorated they could have commemorated
V-ing perfect
I could have been commemorating you could have been commemorating he could have been commemorating we could have been commemorating you could have been commemorating they could have been commemorating
Negation
Simple form
I could not commemorate you could not commemorate he could not commemorate we could not commemorate you could not commemorate they could not commemorate
V-ing form
I could not be commemorating you could not be commemorating he could not be commemorating we could not be commemorating you could not be commemorating they could not be commemorating
Perfect
I could not have commemorated you could not have commemorated he could not have commemorated we could not have commemorated you could not have commemorated they could not have commemorated
V-ing perfect
I could not have been commemorating you could not have been commemorating he could not have been commemorating we could not have been commemorating you could not have been commemorating they could not have been commemorating
Interrogative form
Simple form
could I commemorate? could you commemorate? could he commemorate? could we commemorate? could you commemorate? could they commemorate?
V-ing form
could I be commemorating? could you be commemorating? could he be commemorating? could we be commemorating? could you be commemorating? could they be commemorating?
Perfect
could I have commemorated? could you have commemorated? could he have commemorated? could we have commemorated? could you have commemorated? could they have commemorated?
V-ing perfect
could I have been commemorating? could you have been commemorating? could he have been commemorating? could we have been commemorating? could you have been commemorating? could they have been commemorating?
Interro-negative form
Simple form
could I not commemorate? could you not commemorate? could he not commemorate? could we not commemorate? could you not commemorate? could they not commemorate?
V-ing form
could I not be commemorating? could you not be commemorating? could he not be commemorating? could we not be commemorating? could you not be commemorating? could they not be commemorating?
Perfect
could I not have commemorated? could you not have commemorated? could he not have commemorated? could we not have commemorated? could you not have commemorated? could they not have commemorated?
V-ing perfect
could I not have been commemorating? could you not have been commemorating? could he not have been commemorating? could we not have been commemorating? could you not have been commemorating? could they not have been commemorating?