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