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 couldn't sin you couldn't sin she couldn't sin we couldn't sin you couldn't sin they couldn't sin
V-ing form
I couldn't be sinning you couldn't be sinning she couldn't be sinning we couldn't be sinning you couldn't be sinning they couldn't be sinning
Perfect
I couldn't have sinned you couldn't have sinned she couldn't have sinned we couldn't have sinned you couldn't have sinned they couldn't have sinned
V-ing perfect
I couldn't have been sinning you couldn't have been sinning she couldn't have been sinning we couldn't have been sinning you couldn't have been sinning they couldn't 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
couldn't I sin? couldn't you sin? couldn't she sin? couldn't we sin? couldn't you sin? couldn't they sin?
V-ing form
couldn't I be sinning? couldn't you be sinning? couldn't she be sinning? couldn't we be sinning? couldn't you be sinning? couldn't they be sinning?
Perfect
couldn't I have sinned? couldn't you have sinned? couldn't she have sinned? couldn't we have sinned? couldn't you have sinned? couldn't they have sinned?
V-ing perfect
couldn't I have been sinning? couldn't you have been sinning? couldn't she have been sinning? couldn't we have been sinning? couldn't you have been sinning? couldn't they have been sinning?