could improve
Regular verb: improve - improved- improved

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could improve
you could improve
she could improve
we could improve
you could improve
they could improve 	I could be improving
you could be improving
she could be improving
we could be improving
you could be improving
they could be improving	I could have improved
you could have improved
she could have improved
we could have improved
you could have improved
they could have improved	I could have been improving
you could have been improving
she could have been improving
we could have been improving
you could have been improving
they could have been improving	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I couldn't improve
you couldn't improve
she couldn't improve
we couldn't improve
you couldn't improve
they couldn't improve 	I couldn't be improving
you couldn't be improving
she couldn't be improving
we couldn't be improving
you couldn't be improving
they couldn't be improving	I couldn't have improved
you couldn't have improved
she couldn't have improved
we couldn't have improved
you couldn't have improved
they couldn't have improved	I couldn't have been improving
you couldn't have been improving
she couldn't have been improving
we couldn't have been improving
you couldn't have been improving
they couldn't have been improving	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I improve?
could you improve?
could she improve?
could we improve?
could you improve?
could they improve? 	could I be improving?
could you be improving?
could she be improving?
could we be improving?
could you be improving?
could they be improving? 	could I have improved?
could you have improved?
could she have improved?
could we have improved?
could you have improved?
could they have improved? 	could I have been improving?
could you have been improving?
could she have been improving?
could we have been improving?
could you have been improving?
could they have been improving? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
couldn't I improve?
couldn't you improve?
couldn't she improve?
couldn't we improve?
couldn't you improve?
couldn't they improve? 	couldn't I be improving?
couldn't you be improving?
couldn't she be improving?
couldn't we be improving?
couldn't you be improving?
couldn't they be improving? 	couldn't I have improved?
couldn't you have improved?
couldn't she have improved?
couldn't we have improved?
couldn't you have improved?
couldn't they have improved? 	couldn't I have been improving?
couldn't you have been improving?
couldn't she have been improving?
couldn't we have been improving?
couldn't you have been improving?
couldn't they have been improving?