could persist
Regular verb: persist - persisted- persisted

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could persist
you could persist
she could persist
we could persist
you could persist
they could persist 	I could be persisting
you could be persisting
she could be persisting
we could be persisting
you could be persisting
they could be persisting	I could have persisted
you could have persisted
she could have persisted
we could have persisted
you could have persisted
they could have persisted	I could have been persisting
you could have been persisting
she could have been persisting
we could have been persisting
you could have been persisting
they could have been persisting	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I couldn't persist
you couldn't persist
she couldn't persist
we couldn't persist
you couldn't persist
they couldn't persist 	I couldn't be persisting
you couldn't be persisting
she couldn't be persisting
we couldn't be persisting
you couldn't be persisting
they couldn't be persisting	I couldn't have persisted
you couldn't have persisted
she couldn't have persisted
we couldn't have persisted
you couldn't have persisted
they couldn't have persisted	I couldn't have been persisting
you couldn't have been persisting
she couldn't have been persisting
we couldn't have been persisting
you couldn't have been persisting
they couldn't have been persisting	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I persist?
could you persist?
could she persist?
could we persist?
could you persist?
could they persist? 	could I be persisting?
could you be persisting?
could she be persisting?
could we be persisting?
could you be persisting?
could they be persisting? 	could I have persisted?
could you have persisted?
could she have persisted?
could we have persisted?
could you have persisted?
could they have persisted? 	could I have been persisting?
could you have been persisting?
could she have been persisting?
could we have been persisting?
could you have been persisting?
could they have been persisting? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
couldn't I persist?
couldn't you persist?
couldn't she persist?
couldn't we persist?
couldn't you persist?
couldn't they persist? 	couldn't I be persisting?
couldn't you be persisting?
couldn't she be persisting?
couldn't we be persisting?
couldn't you be persisting?
couldn't they be persisting? 	couldn't I have persisted?
couldn't you have persisted?
couldn't she have persisted?
couldn't we have persisted?
couldn't you have persisted?
couldn't they have persisted? 	couldn't I have been persisting?
couldn't you have been persisting?
couldn't she have been persisting?
couldn't we have been persisting?
couldn't you have been persisting?
couldn't they have been persisting?