I could snigger you could snigger he could snigger we could snigger you could snigger they could snigger
V-ing form
I could be sniggering you could be sniggering he could be sniggering we could be sniggering you could be sniggering they could be sniggering
Perfect
I could have sniggered you could have sniggered he could have sniggered we could have sniggered you could have sniggered they could have sniggered
V-ing perfect
I could have been sniggering you could have been sniggering he could have been sniggering we could have been sniggering you could have been sniggering they could have been sniggering
Negation
Simple form
I could not snigger you could not snigger he could not snigger we could not snigger you could not snigger they could not snigger
V-ing form
I could not be sniggering you could not be sniggering he could not be sniggering we could not be sniggering you could not be sniggering they could not be sniggering
Perfect
I could not have sniggered you could not have sniggered he could not have sniggered we could not have sniggered you could not have sniggered they could not have sniggered
V-ing perfect
I could not have been sniggering you could not have been sniggering he could not have been sniggering we could not have been sniggering you could not have been sniggering they could not have been sniggering
Interrogative form
Simple form
could I snigger? could you snigger? could he snigger? could we snigger? could you snigger? could they snigger?
V-ing form
could I be sniggering? could you be sniggering? could he be sniggering? could we be sniggering? could you be sniggering? could they be sniggering?
Perfect
could I have sniggered? could you have sniggered? could he have sniggered? could we have sniggered? could you have sniggered? could they have sniggered?
V-ing perfect
could I have been sniggering? could you have been sniggering? could he have been sniggering? could we have been sniggering? could you have been sniggering? could they have been sniggering?
Interro-negative form
Simple form
could I not snigger? could you not snigger? could he not snigger? could we not snigger? could you not snigger? could they not snigger?
V-ing form
could I not be sniggering? could you not be sniggering? could he not be sniggering? could we not be sniggering? could you not be sniggering? could they not be sniggering?
Perfect
could I not have sniggered? could you not have sniggered? could he not have sniggered? could we not have sniggered? could you not have sniggered? could they not have sniggered?
V-ing perfect
could I not have been sniggering? could you not have been sniggering? could he not have been sniggering? could we not have been sniggering? could you not have been sniggering? could they not have been sniggering?