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