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