I could attach you could attach she could attach we could attach you could attach they could attach
V-ing form
I could be attaching you could be attaching she could be attaching we could be attaching you could be attaching they could be attaching
Perfect
I could have attached you could have attached she 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 she could have been attaching we could have been attaching you could have been attaching they could have been attaching
Negation
Simple form
I couldn't attach you couldn't attach she couldn't attach we couldn't attach you couldn't attach they couldn't attach
V-ing form
I couldn't be attaching you couldn't be attaching she couldn't be attaching we couldn't be attaching you couldn't be attaching they couldn't be attaching
Perfect
I couldn't have attached you couldn't have attached she couldn't have attached we couldn't have attached you couldn't have attached they couldn't have attached
V-ing perfect
I couldn't have been attaching you couldn't have been attaching she couldn't have been attaching we couldn't have been attaching you couldn't have been attaching they couldn't have been attaching
Interrogative form
Simple form
could I attach? could you attach? could she attach? could we attach? could you attach? could they attach?
V-ing form
could I be attaching? could you be attaching? could she be attaching? could we be attaching? could you be attaching? could they be attaching?
Perfect
could I have attached? could you have attached? could she 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 she have been attaching? could we have been attaching? could you have been attaching? could they have been attaching?
Interro-negative form
Simple form
couldn't I attach? couldn't you attach? couldn't she attach? couldn't we attach? couldn't you attach? couldn't they attach?
V-ing form
couldn't I be attaching? couldn't you be attaching? couldn't she be attaching? couldn't we be attaching? couldn't you be attaching? couldn't they be attaching?
Perfect
couldn't I have attached? couldn't you have attached? couldn't she have attached? couldn't we have attached? couldn't you have attached? couldn't they have attached?
V-ing perfect
couldn't I have been attaching? couldn't you have been attaching? couldn't she have been attaching? couldn't we have been attaching? couldn't you have been attaching? couldn't they have been attaching?