could sue
Regular verb: sue - sued- sued

Affirmation 	
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I could sue
you could sue
she could sue
we could sue
you could sue
they could sue 	I could be suing
you could be suing
she could be suing
we could be suing
you could be suing
they could be suing	I could have sued
you could have sued
she could have sued
we could have sued
you could have sued
they could have sued	I could have been suing
you could have been suing
she could have been suing
we could have been suing
you could have been suing
they could have been suing	

Negation 	
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I couldn't sue
you couldn't sue
she couldn't sue
we couldn't sue
you couldn't sue
they couldn't sue 	I couldn't be suing
you couldn't be suing
she couldn't be suing
we couldn't be suing
you couldn't be suing
they couldn't be suing	I couldn't have sued
you couldn't have sued
she couldn't have sued
we couldn't have sued
you couldn't have sued
they couldn't have sued	I couldn't have been suing
you couldn't have been suing
she couldn't have been suing
we couldn't have been suing
you couldn't have been suing
they couldn't have been suing	

Interrogative form 	
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could I sue?
could you sue?
could she sue?
could we sue?
could you sue?
could they sue? 	could I be suing?
could you be suing?
could she be suing?
could we be suing?
could you be suing?
could they be suing? 	could I have sued?
could you have sued?
could she have sued?
could we have sued?
could you have sued?
could they have sued? 	could I have been suing?
could you have been suing?
could she have been suing?
could we have been suing?
could you have been suing?
could they have been suing? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
couldn't I sue?
couldn't you sue?
couldn't she sue?
couldn't we sue?
couldn't you sue?
couldn't they sue? 	couldn't I be suing?
couldn't you be suing?
couldn't she be suing?
couldn't we be suing?
couldn't you be suing?
couldn't they be suing? 	couldn't I have sued?
couldn't you have sued?
couldn't she have sued?
couldn't we have sued?
couldn't you have sued?
couldn't they have sued? 	couldn't I have been suing?
couldn't you have been suing?
couldn't she have been suing?
couldn't we have been suing?
couldn't you have been suing?
couldn't they have been suing?