I could attach you could attach he could attach we could attach you could attach they could attach
V-ing form
I could be attaching you could be attaching he could be attaching we could be attaching you could be attaching they could be attaching
Perfect
I could have attached you could have attached he could have attached we could have attached you could have attached they could have attached
V-ing perfect
I could have been attaching you could have been attaching he could have been attaching we could have been attaching you could have been attaching they could have been attaching
Negation
Simple form
I could not attach you could not attach he could not attach we could not attach you could not attach they could not attach
V-ing form
I could not be attaching you could not be attaching he could not be attaching we could not be attaching you could not be attaching they could not be attaching
Perfect
I could not have attached you could not have attached he could not have attached we could not have attached you could not have attached they could not have attached
V-ing perfect
I could not have been attaching you could not have been attaching he could not have been attaching we could not have been attaching you could not have been attaching they could not have been attaching
Interrogative form
Simple form
could I attach? could you attach? could he attach? could we attach? could you attach? could they attach?
V-ing form
could I be attaching? could you be attaching? could he be attaching? could we be attaching? could you be attaching? could they be attaching?
Perfect
could I have attached? could you have attached? could he have attached? could we have attached? could you have attached? could they have attached?
V-ing perfect
could I have been attaching? could you have been attaching? could he have been attaching? could we have been attaching? could you have been attaching? could they have been attaching?
Interro-negative form
Simple form
could I not attach? could you not attach? could he not attach? could we not attach? could you not attach? could they not attach?
V-ing form
could I not be attaching? could you not be attaching? could he not be attaching? could we not be attaching? could you not be attaching? could they not be attaching?
Perfect
could I not have attached? could you not have attached? could he not have attached? could we not have attached? could you not have attached? could they not have attached?
V-ing perfect
could I not have been attaching? could you not have been attaching? could he not have been attaching? could we not have been attaching? could you not have been attaching? could they not have been attaching?