I could last you could last she could last we could last you could last they could last
V-ing form
I could be lasting you could be lasting she could be lasting we could be lasting you could be lasting they could be lasting
Perfect
I could have lasted you could have lasted she could have lasted we could have lasted you could have lasted they could have lasted
V-ing perfect
I could have been lasting you could have been lasting she could have been lasting we could have been lasting you could have been lasting they could have been lasting
Negation
Simple form
I could not last you could not last she could not last we could not last you could not last they could not last
V-ing form
I could not be lasting you could not be lasting she could not be lasting we could not be lasting you could not be lasting they could not be lasting
Perfect
I could not have lasted you could not have lasted she could not have lasted we could not have lasted you could not have lasted they could not have lasted
V-ing perfect
I could not have been lasting you could not have been lasting she could not have been lasting we could not have been lasting you could not have been lasting they could not have been lasting
Interrogative form
Simple form
could I last? could you last? could she last? could we last? could you last? could they last?
V-ing form
could I be lasting? could you be lasting? could she be lasting? could we be lasting? could you be lasting? could they be lasting?
Perfect
could I have lasted? could you have lasted? could she have lasted? could we have lasted? could you have lasted? could they have lasted?
V-ing perfect
could I have been lasting? could you have been lasting? could she have been lasting? could we have been lasting? could you have been lasting? could they have been lasting?
Interro-negative form
Simple form
could I not last? could you not last? could she not last? could we not last? could you not last? could they not last?
V-ing form
could I not be lasting? could you not be lasting? could she not be lasting? could we not be lasting? could you not be lasting? could they not be lasting?
Perfect
could I not have lasted? could you not have lasted? could she not have lasted? could we not have lasted? could you not have lasted? could they not have lasted?
V-ing perfect
could I not have been lasting? could you not have been lasting? could she not have been lasting? could we not have been lasting? could you not have been lasting? could they not have been lasting?