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 couldn't last you couldn't last she couldn't last we couldn't last you couldn't last they couldn't last
V-ing form
I couldn't be lasting you couldn't be lasting she couldn't be lasting we couldn't be lasting you couldn't be lasting they couldn't be lasting
Perfect
I couldn't have lasted you couldn't have lasted she couldn't have lasted we couldn't have lasted you couldn't have lasted they couldn't have lasted
V-ing perfect
I couldn't have been lasting you couldn't have been lasting she couldn't have been lasting we couldn't have been lasting you couldn't have been lasting they couldn't 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
couldn't I last? couldn't you last? couldn't she last? couldn't we last? couldn't you last? couldn't they last?
V-ing form
couldn't I be lasting? couldn't you be lasting? couldn't she be lasting? couldn't we be lasting? couldn't you be lasting? couldn't they be lasting?
Perfect
couldn't I have lasted? couldn't you have lasted? couldn't she have lasted? couldn't we have lasted? couldn't you have lasted? couldn't they have lasted?
V-ing perfect
couldn't I have been lasting? couldn't you have been lasting? couldn't she have been lasting? couldn't we have been lasting? couldn't you have been lasting? couldn't they have been lasting?