could unfasten
Regular verb: unfasten - unfastened- unfastened

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could unfasten
you could unfasten
he could unfasten
we could unfasten
you could unfasten
they could unfasten 	I could be unfastening
you could be unfastening
he could be unfastening
we could be unfastening
you could be unfastening
they could be unfastening	I could have unfastened
you could have unfastened
he could have unfastened
we could have unfastened
you could have unfastened
they could have unfastened	I could have been unfastening
you could have been unfastening
he could have been unfastening
we could have been unfastening
you could have been unfastening
they could have been unfastening	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I couldn't unfasten
you couldn't unfasten
he couldn't unfasten
we couldn't unfasten
you couldn't unfasten
they couldn't unfasten 	I couldn't be unfastening
you couldn't be unfastening
he couldn't be unfastening
we couldn't be unfastening
you couldn't be unfastening
they couldn't be unfastening	I couldn't have unfastened
you couldn't have unfastened
he couldn't have unfastened
we couldn't have unfastened
you couldn't have unfastened
they couldn't have unfastened	I couldn't have been unfastening
you couldn't have been unfastening
he couldn't have been unfastening
we couldn't have been unfastening
you couldn't have been unfastening
they couldn't have been unfastening	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I unfasten?
could you unfasten?
could he unfasten?
could we unfasten?
could you unfasten?
could they unfasten? 	could I be unfastening?
could you be unfastening?
could he be unfastening?
could we be unfastening?
could you be unfastening?
could they be unfastening? 	could I have unfastened?
could you have unfastened?
could he have unfastened?
could we have unfastened?
could you have unfastened?
could they have unfastened? 	could I have been unfastening?
could you have been unfastening?
could he have been unfastening?
could we have been unfastening?
could you have been unfastening?
could they have been unfastening? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
couldn't I unfasten?
couldn't you unfasten?
couldn't he unfasten?
couldn't we unfasten?
couldn't you unfasten?
couldn't they unfasten? 	couldn't I be unfastening?
couldn't you be unfastening?
couldn't he be unfastening?
couldn't we be unfastening?
couldn't you be unfastening?
couldn't they be unfastening? 	couldn't I have unfastened?
couldn't you have unfastened?
couldn't he have unfastened?
couldn't we have unfastened?
couldn't you have unfastened?
couldn't they have unfastened? 	couldn't I have been unfastening?
couldn't you have been unfastening?
couldn't he have been unfastening?
couldn't we have been unfastening?
couldn't you have been unfastening?
couldn't they have been unfastening?