I could snigger you could snigger she could snigger we could snigger you could snigger they could snigger
V-ing form
I could be sniggering you could be sniggering she could be sniggering we could be sniggering you could be sniggering they could be sniggering
Perfect
I could have sniggered you could have sniggered she 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 she could have been sniggering we could have been sniggering you could have been sniggering they could have been sniggering
Negation
Simple form
I couldn't snigger you couldn't snigger she couldn't snigger we couldn't snigger you couldn't snigger they couldn't snigger
V-ing form
I couldn't be sniggering you couldn't be sniggering she couldn't be sniggering we couldn't be sniggering you couldn't be sniggering they couldn't be sniggering
Perfect
I couldn't have sniggered you couldn't have sniggered she couldn't have sniggered we couldn't have sniggered you couldn't have sniggered they couldn't have sniggered
V-ing perfect
I couldn't have been sniggering you couldn't have been sniggering she couldn't have been sniggering we couldn't have been sniggering you couldn't have been sniggering they couldn't have been sniggering
Interrogative form
Simple form
could I snigger? could you snigger? could she snigger? could we snigger? could you snigger? could they snigger?
V-ing form
could I be sniggering? could you be sniggering? could she be sniggering? could we be sniggering? could you be sniggering? could they be sniggering?
Perfect
could I have sniggered? could you have sniggered? could she 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 she have been sniggering? could we have been sniggering? could you have been sniggering? could they have been sniggering?
Interro-negative form
Simple form
couldn't I snigger? couldn't you snigger? couldn't she snigger? couldn't we snigger? couldn't you snigger? couldn't they snigger?
V-ing form
couldn't I be sniggering? couldn't you be sniggering? couldn't she be sniggering? couldn't we be sniggering? couldn't you be sniggering? couldn't they be sniggering?
Perfect
couldn't I have sniggered? couldn't you have sniggered? couldn't she have sniggered? couldn't we have sniggered? couldn't you have sniggered? couldn't they have sniggered?
V-ing perfect
couldn't I have been sniggering? couldn't you have been sniggering? couldn't she have been sniggering? couldn't we have been sniggering? couldn't you have been sniggering? couldn't they have been sniggering?