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