I could frock you could frock he could frock we could frock you could frock they could frock
V-ing form
I could be frocking you could be frocking he could be frocking we could be frocking you could be frocking they could be frocking
Perfect
I could have frocked you could have frocked he could have frocked we could have frocked you could have frocked they could have frocked
V-ing perfect
I could have been frocking you could have been frocking he could have been frocking we could have been frocking you could have been frocking they could have been frocking
Negation
Simple form
I could not frock you could not frock he could not frock we could not frock you could not frock they could not frock
V-ing form
I could not be frocking you could not be frocking he could not be frocking we could not be frocking you could not be frocking they could not be frocking
Perfect
I could not have frocked you could not have frocked he could not have frocked we could not have frocked you could not have frocked they could not have frocked
V-ing perfect
I could not have been frocking you could not have been frocking he could not have been frocking we could not have been frocking you could not have been frocking they could not have been frocking
Interrogative form
Simple form
could I frock? could you frock? could he frock? could we frock? could you frock? could they frock?
V-ing form
could I be frocking? could you be frocking? could he be frocking? could we be frocking? could you be frocking? could they be frocking?
Perfect
could I have frocked? could you have frocked? could he have frocked? could we have frocked? could you have frocked? could they have frocked?
V-ing perfect
could I have been frocking? could you have been frocking? could he have been frocking? could we have been frocking? could you have been frocking? could they have been frocking?
Interro-negative form
Simple form
could I not frock? could you not frock? could he not frock? could we not frock? could you not frock? could they not frock?
V-ing form
could I not be frocking? could you not be frocking? could he not be frocking? could we not be frocking? could you not be frocking? could they not be frocking?
Perfect
could I not have frocked? could you not have frocked? could he not have frocked? could we not have frocked? could you not have frocked? could they not have frocked?
V-ing perfect
could I not have been frocking? could you not have been frocking? could he not have been frocking? could we not have been frocking? could you not have been frocking? could they not have been frocking?