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