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