I could blank you could blank he could blank we could blank you could blank they could blank
V-ing form
I could be blanking you could be blanking he could be blanking we could be blanking you could be blanking they could be blanking
Perfect
I could have blanked you could have blanked he could have blanked we could have blanked you could have blanked they could have blanked
V-ing perfect
I could have been blanking you could have been blanking he could have been blanking we could have been blanking you could have been blanking they could have been blanking
Negation
Simple form
I could not blank you could not blank he could not blank we could not blank you could not blank they could not blank
V-ing form
I could not be blanking you could not be blanking he could not be blanking we could not be blanking you could not be blanking they could not be blanking
Perfect
I could not have blanked you could not have blanked he could not have blanked we could not have blanked you could not have blanked they could not have blanked
V-ing perfect
I could not have been blanking you could not have been blanking he could not have been blanking we could not have been blanking you could not have been blanking they could not have been blanking
Interrogative form
Simple form
could I blank? could you blank? could he blank? could we blank? could you blank? could they blank?
V-ing form
could I be blanking? could you be blanking? could he be blanking? could we be blanking? could you be blanking? could they be blanking?
Perfect
could I have blanked? could you have blanked? could he have blanked? could we have blanked? could you have blanked? could they have blanked?
V-ing perfect
could I have been blanking? could you have been blanking? could he have been blanking? could we have been blanking? could you have been blanking? could they have been blanking?
Interro-negative form
Simple form
could I not blank? could you not blank? could he not blank? could we not blank? could you not blank? could they not blank?
V-ing form
could I not be blanking? could you not be blanking? could he not be blanking? could we not be blanking? could you not be blanking? could they not be blanking?
Perfect
could I not have blanked? could you not have blanked? could he not have blanked? could we not have blanked? could you not have blanked? could they not have blanked?
V-ing perfect
could I not have been blanking? could you not have been blanking? could he not have been blanking? could we not have been blanking? could you not have been blanking? could they not have been blanking?