I can backcheck you can backcheck she can backcheck we can backcheck you can backcheck they can backcheck
V-ing form
I can be backchecking you can be backchecking she can be backchecking we can be backchecking you can be backchecking they can be backchecking
Perfect
I can have backchecked you can have backchecked she can have backchecked we can have backchecked you can have backchecked they can have backchecked
V-ing perfect
I can have been backchecking you can have been backchecking she can have been backchecking we can have been backchecking you can have been backchecking they can have been backchecking
Negation
Simple form
I cannot backcheck you cannot backcheck she cannot backcheck we cannot backcheck you cannot backcheck they cannot backcheck
V-ing form
I cannot be backchecking you cannot be backchecking she cannot be backchecking we cannot be backchecking you cannot be backchecking they cannot be backchecking
Perfect
I cannot have backchecked you cannot have backchecked she cannot have backchecked we cannot have backchecked you cannot have backchecked they cannot have backchecked
V-ing perfect
I cannot have been backchecking you cannot have been backchecking she cannot have been backchecking we cannot have been backchecking you cannot have been backchecking they cannot have been backchecking
Interrogative form
Simple form
can I backcheck? can you backcheck? can she backcheck? can we backcheck? can you backcheck? can they backcheck?
V-ing form
can I be backchecking? can you be backchecking? can she be backchecking? can we be backchecking? can you be backchecking? can they be backchecking?
Perfect
can I have backchecked? can you have backchecked? can she have backchecked? can we have backchecked? can you have backchecked? can they have backchecked?
V-ing perfect
can I have been backchecking? can you have been backchecking? can she have been backchecking? can we have been backchecking? can you have been backchecking? can they have been backchecking?
Interro-negative form
Simple form
can I not backcheck? can you not backcheck? can she not backcheck? can we not backcheck? can you not backcheck? can they not backcheck?
V-ing form
can I not be backchecking? can you not be backchecking? can she not be backchecking? can we not be backchecking? can you not be backchecking? can they not be backchecking?
Perfect
can I not have backchecked? can you not have backchecked? can she not have backchecked? can we not have backchecked? can you not have backchecked? can they not have backchecked?
V-ing perfect
can I not have been backchecking? can you not have been backchecking? can she not have been backchecking? can we not have been backchecking? can you not have been backchecking? can they not have been backchecking?