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