could cause
Regular verb: cause - caused- caused

Affirmation 	
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I could cause
you could cause
he could cause
we could cause
you could cause
they could cause 	I could be causing
you could be causing
he could be causing
we could be causing
you could be causing
they could be causing	I could have caused
you could have caused
he could have caused
we could have caused
you could have caused
they could have caused	I could have been causing
you could have been causing
he could have been causing
we could have been causing
you could have been causing
they could have been causing	

Negation 	
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I couldn't cause
you couldn't cause
he couldn't cause
we couldn't cause
you couldn't cause
they couldn't cause 	I couldn't be causing
you couldn't be causing
he couldn't be causing
we couldn't be causing
you couldn't be causing
they couldn't be causing	I couldn't have caused
you couldn't have caused
he couldn't have caused
we couldn't have caused
you couldn't have caused
they couldn't have caused	I couldn't have been causing
you couldn't have been causing
he couldn't have been causing
we couldn't have been causing
you couldn't have been causing
they couldn't have been causing	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I cause?
could you cause?
could he cause?
could we cause?
could you cause?
could they cause? 	could I be causing?
could you be causing?
could he be causing?
could we be causing?
could you be causing?
could they be causing? 	could I have caused?
could you have caused?
could he have caused?
could we have caused?
could you have caused?
could they have caused? 	could I have been causing?
could you have been causing?
could he have been causing?
could we have been causing?
could you have been causing?
could they have been causing? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
couldn't I cause?
couldn't you cause?
couldn't he cause?
couldn't we cause?
couldn't you cause?
couldn't they cause? 	couldn't I be causing?
couldn't you be causing?
couldn't he be causing?
couldn't we be causing?
couldn't you be causing?
couldn't they be causing? 	couldn't I have caused?
couldn't you have caused?
couldn't he have caused?
couldn't we have caused?
couldn't you have caused?
couldn't they have caused? 	couldn't I have been causing?
couldn't you have been causing?
couldn't he have been causing?
couldn't we have been causing?
couldn't you have been causing?
couldn't they have been causing?