could invigilate
Regular verb: invigilate - invigilated- invigilated

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could invigilate
you could invigilate
he could invigilate
we could invigilate
you could invigilate
they could invigilate 	I could be invigilating
you could be invigilating
he could be invigilating
we could be invigilating
you could be invigilating
they could be invigilating	I could have invigilated
you could have invigilated
he could have invigilated
we could have invigilated
you could have invigilated
they could have invigilated	I could have been invigilating
you could have been invigilating
he could have been invigilating
we could have been invigilating
you could have been invigilating
they could have been invigilating	

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

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