could study
Regular verb: study - studied- studied

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could study
you could study
he could study
we could study
you could study
they could study 	I could be studying
you could be studying
he could be studying
we could be studying
you could be studying
they could be studying	I could have studied
you could have studied
he could have studied
we could have studied
you could have studied
they could have studied	I could have been studying
you could have been studying
he could have been studying
we could have been studying
you could have been studying
they could have been studying	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I couldn't study
you couldn't study
he couldn't study
we couldn't study
you couldn't study
they couldn't study 	I couldn't be studying
you couldn't be studying
he couldn't be studying
we couldn't be studying
you couldn't be studying
they couldn't be studying	I couldn't have studied
you couldn't have studied
he couldn't have studied
we couldn't have studied
you couldn't have studied
they couldn't have studied	I couldn't have been studying
you couldn't have been studying
he couldn't have been studying
we couldn't have been studying
you couldn't have been studying
they couldn't have been studying	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I study?
could you study?
could he study?
could we study?
could you study?
could they study? 	could I be studying?
could you be studying?
could he be studying?
could we be studying?
could you be studying?
could they be studying? 	could I have studied?
could you have studied?
could he have studied?
could we have studied?
could you have studied?
could they have studied? 	could I have been studying?
could you have been studying?
could he have been studying?
could we have been studying?
could you have been studying?
could they have been studying? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
couldn't I study?
couldn't you study?
couldn't he study?
couldn't we study?
couldn't you study?
couldn't they study? 	couldn't I be studying?
couldn't you be studying?
couldn't he be studying?
couldn't we be studying?
couldn't you be studying?
couldn't they be studying? 	couldn't I have studied?
couldn't you have studied?
couldn't he have studied?
couldn't we have studied?
couldn't you have studied?
couldn't they have studied? 	couldn't I have been studying?
couldn't you have been studying?
couldn't he have been studying?
couldn't we have been studying?
couldn't you have been studying?
couldn't they have been studying?