could unscrew
Regular verb: unscrew - unscrewed- unscrewed

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could unscrew
you could unscrew
she could unscrew
we could unscrew
you could unscrew
they could unscrew 	I could be unscrewing
you could be unscrewing
she could be unscrewing
we could be unscrewing
you could be unscrewing
they could be unscrewing	I could have unscrewed
you could have unscrewed
she could have unscrewed
we could have unscrewed
you could have unscrewed
they could have unscrewed	I could have been unscrewing
you could have been unscrewing
she could have been unscrewing
we could have been unscrewing
you could have been unscrewing
they could have been unscrewing	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I couldn't unscrew
you couldn't unscrew
she couldn't unscrew
we couldn't unscrew
you couldn't unscrew
they couldn't unscrew 	I couldn't be unscrewing
you couldn't be unscrewing
she couldn't be unscrewing
we couldn't be unscrewing
you couldn't be unscrewing
they couldn't be unscrewing	I couldn't have unscrewed
you couldn't have unscrewed
she couldn't have unscrewed
we couldn't have unscrewed
you couldn't have unscrewed
they couldn't have unscrewed	I couldn't have been unscrewing
you couldn't have been unscrewing
she couldn't have been unscrewing
we couldn't have been unscrewing
you couldn't have been unscrewing
they couldn't have been unscrewing	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I unscrew?
could you unscrew?
could she unscrew?
could we unscrew?
could you unscrew?
could they unscrew? 	could I be unscrewing?
could you be unscrewing?
could she be unscrewing?
could we be unscrewing?
could you be unscrewing?
could they be unscrewing? 	could I have unscrewed?
could you have unscrewed?
could she have unscrewed?
could we have unscrewed?
could you have unscrewed?
could they have unscrewed? 	could I have been unscrewing?
could you have been unscrewing?
could she have been unscrewing?
could we have been unscrewing?
could you have been unscrewing?
could they have been unscrewing? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
couldn't I unscrew?
couldn't you unscrew?
couldn't she unscrew?
couldn't we unscrew?
couldn't you unscrew?
couldn't they unscrew? 	couldn't I be unscrewing?
couldn't you be unscrewing?
couldn't she be unscrewing?
couldn't we be unscrewing?
couldn't you be unscrewing?
couldn't they be unscrewing? 	couldn't I have unscrewed?
couldn't you have unscrewed?
couldn't she have unscrewed?
couldn't we have unscrewed?
couldn't you have unscrewed?
couldn't they have unscrewed? 	couldn't I have been unscrewing?
couldn't you have been unscrewing?
couldn't she have been unscrewing?
couldn't we have been unscrewing?
couldn't you have been unscrewing?
couldn't they have been unscrewing?