could circulate
Regular verb: circulate - circulated- circulated

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could circulate
you could circulate
she could circulate
we could circulate
you could circulate
they could circulate 	I could be circulating
you could be circulating
she could be circulating
we could be circulating
you could be circulating
they could be circulating	I could have circulated
you could have circulated
she could have circulated
we could have circulated
you could have circulated
they could have circulated	I could have been circulating
you could have been circulating
she could have been circulating
we could have been circulating
you could have been circulating
they could have been circulating	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I couldn't circulate
you couldn't circulate
she couldn't circulate
we couldn't circulate
you couldn't circulate
they couldn't circulate 	I couldn't be circulating
you couldn't be circulating
she couldn't be circulating
we couldn't be circulating
you couldn't be circulating
they couldn't be circulating	I couldn't have circulated
you couldn't have circulated
she couldn't have circulated
we couldn't have circulated
you couldn't have circulated
they couldn't have circulated	I couldn't have been circulating
you couldn't have been circulating
she couldn't have been circulating
we couldn't have been circulating
you couldn't have been circulating
they couldn't have been circulating	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I circulate?
could you circulate?
could she circulate?
could we circulate?
could you circulate?
could they circulate? 	could I be circulating?
could you be circulating?
could she be circulating?
could we be circulating?
could you be circulating?
could they be circulating? 	could I have circulated?
could you have circulated?
could she have circulated?
could we have circulated?
could you have circulated?
could they have circulated? 	could I have been circulating?
could you have been circulating?
could she have been circulating?
could we have been circulating?
could you have been circulating?
could they have been circulating? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
couldn't I circulate?
couldn't you circulate?
couldn't she circulate?
couldn't we circulate?
couldn't you circulate?
couldn't they circulate? 	couldn't I be circulating?
couldn't you be circulating?
couldn't she be circulating?
couldn't we be circulating?
couldn't you be circulating?
couldn't they be circulating? 	couldn't I have circulated?
couldn't you have circulated?
couldn't she have circulated?
couldn't we have circulated?
couldn't you have circulated?
couldn't they have circulated? 	couldn't I have been circulating?
couldn't you have been circulating?
couldn't she have been circulating?
couldn't we have been circulating?
couldn't you have been circulating?
couldn't they have been circulating?