I could backcross you could backcross she could backcross we could backcross you could backcross they could backcross
V-ing form
I could be backcrossing you could be backcrossing she could be backcrossing we could be backcrossing you could be backcrossing they could be backcrossing
Perfect
I could have backcrossed you could have backcrossed she could have backcrossed we could have backcrossed you could have backcrossed they could have backcrossed
V-ing perfect
I could have been backcrossing you could have been backcrossing she could have been backcrossing we could have been backcrossing you could have been backcrossing they could have been backcrossing
Negation
Simple form
I could not backcross you could not backcross she could not backcross we could not backcross you could not backcross they could not backcross
V-ing form
I could not be backcrossing you could not be backcrossing she could not be backcrossing we could not be backcrossing you could not be backcrossing they could not be backcrossing
Perfect
I could not have backcrossed you could not have backcrossed she could not have backcrossed we could not have backcrossed you could not have backcrossed they could not have backcrossed
V-ing perfect
I could not have been backcrossing you could not have been backcrossing she could not have been backcrossing we could not have been backcrossing you could not have been backcrossing they could not have been backcrossing
Interrogative form
Simple form
could I backcross? could you backcross? could she backcross? could we backcross? could you backcross? could they backcross?
V-ing form
could I be backcrossing? could you be backcrossing? could she be backcrossing? could we be backcrossing? could you be backcrossing? could they be backcrossing?
Perfect
could I have backcrossed? could you have backcrossed? could she have backcrossed? could we have backcrossed? could you have backcrossed? could they have backcrossed?
V-ing perfect
could I have been backcrossing? could you have been backcrossing? could she have been backcrossing? could we have been backcrossing? could you have been backcrossing? could they have been backcrossing?
Interro-negative form
Simple form
could I not backcross? could you not backcross? could she not backcross? could we not backcross? could you not backcross? could they not backcross?
V-ing form
could I not be backcrossing? could you not be backcrossing? could she not be backcrossing? could we not be backcrossing? could you not be backcrossing? could they not be backcrossing?
Perfect
could I not have backcrossed? could you not have backcrossed? could she not have backcrossed? could we not have backcrossed? could you not have backcrossed? could they not have backcrossed?
V-ing perfect
could I not have been backcrossing? could you not have been backcrossing? could she not have been backcrossing? could we not have been backcrossing? could you not have been backcrossing? could they not have been backcrossing?