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