I could shorten you could shorten she could shorten we could shorten you could shorten they could shorten
V-ing form
I could be shortening you could be shortening she could be shortening we could be shortening you could be shortening they could be shortening
Perfect
I could have shortened you could have shortened she could have shortened we could have shortened you could have shortened they could have shortened
V-ing perfect
I could have been shortening you could have been shortening she could have been shortening we could have been shortening you could have been shortening they could have been shortening
Negation
Simple form
I could not shorten you could not shorten she could not shorten we could not shorten you could not shorten they could not shorten
V-ing form
I could not be shortening you could not be shortening she could not be shortening we could not be shortening you could not be shortening they could not be shortening
Perfect
I could not have shortened you could not have shortened she could not have shortened we could not have shortened you could not have shortened they could not have shortened
V-ing perfect
I could not have been shortening you could not have been shortening she could not have been shortening we could not have been shortening you could not have been shortening they could not have been shortening
Interrogative form
Simple form
could I shorten? could you shorten? could she shorten? could we shorten? could you shorten? could they shorten?
V-ing form
could I be shortening? could you be shortening? could she be shortening? could we be shortening? could you be shortening? could they be shortening?
Perfect
could I have shortened? could you have shortened? could she have shortened? could we have shortened? could you have shortened? could they have shortened?
V-ing perfect
could I have been shortening? could you have been shortening? could she have been shortening? could we have been shortening? could you have been shortening? could they have been shortening?
Interro-negative form
Simple form
could I not shorten? could you not shorten? could she not shorten? could we not shorten? could you not shorten? could they not shorten?
V-ing form
could I not be shortening? could you not be shortening? could she not be shortening? could we not be shortening? could you not be shortening? could they not be shortening?
Perfect
could I not have shortened? could you not have shortened? could she not have shortened? could we not have shortened? could you not have shortened? could they not have shortened?
V-ing perfect
could I not have been shortening? could you not have been shortening? could she not have been shortening? could we not have been shortening? could you not have been shortening? could they not have been shortening?