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 couldn't backcross you couldn't backcross she couldn't backcross we couldn't backcross you couldn't backcross they couldn't backcross
V-ing form
I couldn't be backcrossing you couldn't be backcrossing she couldn't be backcrossing we couldn't be backcrossing you couldn't be backcrossing they couldn't be backcrossing
Perfect
I couldn't have backcrossed you couldn't have backcrossed she couldn't have backcrossed we couldn't have backcrossed you couldn't have backcrossed they couldn't have backcrossed
V-ing perfect
I couldn't have been backcrossing you couldn't have been backcrossing she couldn't have been backcrossing we couldn't have been backcrossing you couldn't have been backcrossing they couldn't 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
couldn't I backcross? couldn't you backcross? couldn't she backcross? couldn't we backcross? couldn't you backcross? couldn't they backcross?
V-ing form
couldn't I be backcrossing? couldn't you be backcrossing? couldn't she be backcrossing? couldn't we be backcrossing? couldn't you be backcrossing? couldn't they be backcrossing?
Perfect
couldn't I have backcrossed? couldn't you have backcrossed? couldn't she have backcrossed? couldn't we have backcrossed? couldn't you have backcrossed? couldn't they have backcrossed?
V-ing perfect
couldn't I have been backcrossing? couldn't you have been backcrossing? couldn't she have been backcrossing? couldn't we have been backcrossing? couldn't you have been backcrossing? couldn't they have been backcrossing?