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 could not clatter you could not clatter he could not clatter we could not clatter you could not clatter they could not clatter
V-ing form
I could not be clattering you could not be clattering he could not be clattering we could not be clattering you could not be clattering they could not be clattering
Perfect
I could not have clattered you could not have clattered he could not have clattered we could not have clattered you could not have clattered they could not have clattered
V-ing perfect
I could not have been clattering you could not have been clattering he could not have been clattering we could not have been clattering you could not have been clattering they could not 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
could I not clatter? could you not clatter? could he not clatter? could we not clatter? could you not clatter? could they not clatter?
V-ing form
could I not be clattering? could you not be clattering? could he not be clattering? could we not be clattering? could you not be clattering? could they not be clattering?
Perfect
could I not have clattered? could you not have clattered? could he not have clattered? could we not have clattered? could you not have clattered? could they not have clattered?
V-ing perfect
could I not have been clattering? could you not have been clattering? could he not have been clattering? could we not have been clattering? could you not have been clattering? could they not have been clattering?