could thank
Regular verb: thank - thanked- thanked

Affirmation 	
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I could thank
you could thank
he could thank
we could thank
you could thank
they could thank 	I could be thanking
you could be thanking
he could be thanking
we could be thanking
you could be thanking
they could be thanking	I could have thanked
you could have thanked
he could have thanked
we could have thanked
you could have thanked
they could have thanked	I could have been thanking
you could have been thanking
he could have been thanking
we could have been thanking
you could have been thanking
they could have been thanking	

Negation 	
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I couldn't thank
you couldn't thank
he couldn't thank
we couldn't thank
you couldn't thank
they couldn't thank 	I couldn't be thanking
you couldn't be thanking
he couldn't be thanking
we couldn't be thanking
you couldn't be thanking
they couldn't be thanking	I couldn't have thanked
you couldn't have thanked
he couldn't have thanked
we couldn't have thanked
you couldn't have thanked
they couldn't have thanked	I couldn't have been thanking
you couldn't have been thanking
he couldn't have been thanking
we couldn't have been thanking
you couldn't have been thanking
they couldn't have been thanking	

Interrogative form 	
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could I thank?
could you thank?
could he thank?
could we thank?
could you thank?
could they thank? 	could I be thanking?
could you be thanking?
could he be thanking?
could we be thanking?
could you be thanking?
could they be thanking? 	could I have thanked?
could you have thanked?
could he have thanked?
could we have thanked?
could you have thanked?
could they have thanked? 	could I have been thanking?
could you have been thanking?
could he have been thanking?
could we have been thanking?
could you have been thanking?
could they have been thanking? 	

Interro-negative form 	
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couldn't I thank?
couldn't you thank?
couldn't he thank?
couldn't we thank?
couldn't you thank?
couldn't they thank? 	couldn't I be thanking?
couldn't you be thanking?
couldn't he be thanking?
couldn't we be thanking?
couldn't you be thanking?
couldn't they be thanking? 	couldn't I have thanked?
couldn't you have thanked?
couldn't he have thanked?
couldn't we have thanked?
couldn't you have thanked?
couldn't they have thanked? 	couldn't I have been thanking?
couldn't you have been thanking?
couldn't he have been thanking?
couldn't we have been thanking?
couldn't you have been thanking?
couldn't they have been thanking?