I could post you could post she could post we could post you could post they could post
V-ing form
I could be posting you could be posting she could be posting we could be posting you could be posting they could be posting
Perfect
I could have posted you could have posted she could have posted we could have posted you could have posted they could have posted
V-ing perfect
I could have been posting you could have been posting she could have been posting we could have been posting you could have been posting they could have been posting
Negation
Simple form
I could not post you could not post she could not post we could not post you could not post they could not post
V-ing form
I could not be posting you could not be posting she could not be posting we could not be posting you could not be posting they could not be posting
Perfect
I could not have posted you could not have posted she could not have posted we could not have posted you could not have posted they could not have posted
V-ing perfect
I could not have been posting you could not have been posting she could not have been posting we could not have been posting you could not have been posting they could not have been posting
Interrogative form
Simple form
could I post? could you post? could she post? could we post? could you post? could they post?
V-ing form
could I be posting? could you be posting? could she be posting? could we be posting? could you be posting? could they be posting?
Perfect
could I have posted? could you have posted? could she have posted? could we have posted? could you have posted? could they have posted?
V-ing perfect
could I have been posting? could you have been posting? could she have been posting? could we have been posting? could you have been posting? could they have been posting?
Interro-negative form
Simple form
could I not post? could you not post? could she not post? could we not post? could you not post? could they not post?
V-ing form
could I not be posting? could you not be posting? could she not be posting? could we not be posting? could you not be posting? could they not be posting?
Perfect
could I not have posted? could you not have posted? could she not have posted? could we not have posted? could you not have posted? could they not have posted?
V-ing perfect
could I not have been posting? could you not have been posting? could she not have been posting? could we not have been posting? could you not have been posting? could they not have been posting?