I could clatter you could clatter she could clatter we could clatter you could clatter they could clatter
V-ing form
I could be clattering you could be clattering she could be clattering we could be clattering you could be clattering they could be clattering
Perfect
I could have clattered you could have clattered she 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 she 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 she 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 she 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 she 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 she 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 she clatter? could we clatter? could you clatter? could they clatter?
V-ing form
could I be clattering? could you be clattering? could she be clattering? could we be clattering? could you be clattering? could they be clattering?
Perfect
could I have clattered? could you have clattered? could she 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 she 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 she 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 she 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 she 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 she have been clattering? couldn't we have been clattering? couldn't you have been clattering? couldn't they have been clattering?