could croak
Regular verb: croak - croaked- croaked

Affirmation 	
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I could croak
you could croak
she could croak
we could croak
you could croak
they could croak 	I could be croaking
you could be croaking
she could be croaking
we could be croaking
you could be croaking
they could be croaking	I could have croaked
you could have croaked
she could have croaked
we could have croaked
you could have croaked
they could have croaked	I could have been croaking
you could have been croaking
she could have been croaking
we could have been croaking
you could have been croaking
they could have been croaking	

Negation 	
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I couldn't croak
you couldn't croak
she couldn't croak
we couldn't croak
you couldn't croak
they couldn't croak 	I couldn't be croaking
you couldn't be croaking
she couldn't be croaking
we couldn't be croaking
you couldn't be croaking
they couldn't be croaking	I couldn't have croaked
you couldn't have croaked
she couldn't have croaked
we couldn't have croaked
you couldn't have croaked
they couldn't have croaked	I couldn't have been croaking
you couldn't have been croaking
she couldn't have been croaking
we couldn't have been croaking
you couldn't have been croaking
they couldn't have been croaking	

Interrogative form 	
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could I croak?
could you croak?
could she croak?
could we croak?
could you croak?
could they croak? 	could I be croaking?
could you be croaking?
could she be croaking?
could we be croaking?
could you be croaking?
could they be croaking? 	could I have croaked?
could you have croaked?
could she have croaked?
could we have croaked?
could you have croaked?
could they have croaked? 	could I have been croaking?
could you have been croaking?
could she have been croaking?
could we have been croaking?
could you have been croaking?
could they have been croaking? 	

Interro-negative form 	
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couldn't I croak?
couldn't you croak?
couldn't she croak?
couldn't we croak?
couldn't you croak?
couldn't they croak? 	couldn't I be croaking?
couldn't you be croaking?
couldn't she be croaking?
couldn't we be croaking?
couldn't you be croaking?
couldn't they be croaking? 	couldn't I have croaked?
couldn't you have croaked?
couldn't she have croaked?
couldn't we have croaked?
couldn't you have croaked?
couldn't they have croaked? 	couldn't I have been croaking?
couldn't you have been croaking?
couldn't she have been croaking?
couldn't we have been croaking?
couldn't you have been croaking?
couldn't they have been croaking?