I could busk you could busk she could busk we could busk you could busk they could busk
V-ing form
I could be busking you could be busking she could be busking we could be busking you could be busking they could be busking
Perfect
I could have busked you could have busked she could have busked we could have busked you could have busked they could have busked
V-ing perfect
I could have been busking you could have been busking she could have been busking we could have been busking you could have been busking they could have been busking
Negation
Simple form
I could not busk you could not busk she could not busk we could not busk you could not busk they could not busk
V-ing form
I could not be busking you could not be busking she could not be busking we could not be busking you could not be busking they could not be busking
Perfect
I could not have busked you could not have busked she could not have busked we could not have busked you could not have busked they could not have busked
V-ing perfect
I could not have been busking you could not have been busking she could not have been busking we could not have been busking you could not have been busking they could not have been busking
Interrogative form
Simple form
could I busk? could you busk? could she busk? could we busk? could you busk? could they busk?
V-ing form
could I be busking? could you be busking? could she be busking? could we be busking? could you be busking? could they be busking?
Perfect
could I have busked? could you have busked? could she have busked? could we have busked? could you have busked? could they have busked?
V-ing perfect
could I have been busking? could you have been busking? could she have been busking? could we have been busking? could you have been busking? could they have been busking?
Interro-negative form
Simple form
could I not busk? could you not busk? could she not busk? could we not busk? could you not busk? could they not busk?
V-ing form
could I not be busking? could you not be busking? could she not be busking? could we not be busking? could you not be busking? could they not be busking?
Perfect
could I not have busked? could you not have busked? could she not have busked? could we not have busked? could you not have busked? could they not have busked?
V-ing perfect
could I not have been busking? could you not have been busking? could she not have been busking? could we not have been busking? could you not have been busking? could they not have been busking?