I could sin you could sin she could sin we could sin you could sin they could sin
V-ing form
I could be sinning you could be sinning she could be sinning we could be sinning you could be sinning they could be sinning
Perfect
I could have sinned you could have sinned she could have sinned we could have sinned you could have sinned they could have sinned
V-ing perfect
I could have been sinning you could have been sinning she could have been sinning we could have been sinning you could have been sinning they could have been sinning
Negation
Simple form
I could not sin you could not sin she could not sin we could not sin you could not sin they could not sin
V-ing form
I could not be sinning you could not be sinning she could not be sinning we could not be sinning you could not be sinning they could not be sinning
Perfect
I could not have sinned you could not have sinned she could not have sinned we could not have sinned you could not have sinned they could not have sinned
V-ing perfect
I could not have been sinning you could not have been sinning she could not have been sinning we could not have been sinning you could not have been sinning they could not have been sinning
Interrogative form
Simple form
could I sin? could you sin? could she sin? could we sin? could you sin? could they sin?
V-ing form
could I be sinning? could you be sinning? could she be sinning? could we be sinning? could you be sinning? could they be sinning?
Perfect
could I have sinned? could you have sinned? could she have sinned? could we have sinned? could you have sinned? could they have sinned?
V-ing perfect
could I have been sinning? could you have been sinning? could she have been sinning? could we have been sinning? could you have been sinning? could they have been sinning?
Interro-negative form
Simple form
could I not sin? could you not sin? could she not sin? could we not sin? could you not sin? could they not sin?
V-ing form
could I not be sinning? could you not be sinning? could she not be sinning? could we not be sinning? could you not be sinning? could they not be sinning?
Perfect
could I not have sinned? could you not have sinned? could she not have sinned? could we not have sinned? could you not have sinned? could they not have sinned?
V-ing perfect
could I not have been sinning? could you not have been sinning? could she not have been sinning? could we not have been sinning? could you not have been sinning? could they not have been sinning?