I could skin you could skin he could skin we could skin you could skin they could skin
V-ing form
I could be skinning you could be skinning he could be skinning we could be skinning you could be skinning they could be skinning
Perfect
I could have skinned you could have skinned he could have skinned we could have skinned you could have skinned they could have skinned
V-ing perfect
I could have been skinning you could have been skinning he could have been skinning we could have been skinning you could have been skinning they could have been skinning
Negation
Simple form
I couldn't skin you couldn't skin he couldn't skin we couldn't skin you couldn't skin they couldn't skin
V-ing form
I couldn't be skinning you couldn't be skinning he couldn't be skinning we couldn't be skinning you couldn't be skinning they couldn't be skinning
Perfect
I couldn't have skinned you couldn't have skinned he couldn't have skinned we couldn't have skinned you couldn't have skinned they couldn't have skinned
V-ing perfect
I couldn't have been skinning you couldn't have been skinning he couldn't have been skinning we couldn't have been skinning you couldn't have been skinning they couldn't have been skinning
Interrogative form
Simple form
could I skin? could you skin? could he skin? could we skin? could you skin? could they skin?
V-ing form
could I be skinning? could you be skinning? could he be skinning? could we be skinning? could you be skinning? could they be skinning?
Perfect
could I have skinned? could you have skinned? could he have skinned? could we have skinned? could you have skinned? could they have skinned?
V-ing perfect
could I have been skinning? could you have been skinning? could he have been skinning? could we have been skinning? could you have been skinning? could they have been skinning?
Interro-negative form
Simple form
couldn't I skin? couldn't you skin? couldn't he skin? couldn't we skin? couldn't you skin? couldn't they skin?
V-ing form
couldn't I be skinning? couldn't you be skinning? couldn't he be skinning? couldn't we be skinning? couldn't you be skinning? couldn't they be skinning?
Perfect
couldn't I have skinned? couldn't you have skinned? couldn't he have skinned? couldn't we have skinned? couldn't you have skinned? couldn't they have skinned?
V-ing perfect
couldn't I have been skinning? couldn't you have been skinning? couldn't he have been skinning? couldn't we have been skinning? couldn't you have been skinning? couldn't they have been skinning?