could unlock
Regular verb: unlock - unlocked- unlocked

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could unlock
you could unlock
he could unlock
we could unlock
you could unlock
they could unlock 	I could be unlocking
you could be unlocking
he could be unlocking
we could be unlocking
you could be unlocking
they could be unlocking	I could have unlocked
you could have unlocked
he could have unlocked
we could have unlocked
you could have unlocked
they could have unlocked	I could have been unlocking
you could have been unlocking
he could have been unlocking
we could have been unlocking
you could have been unlocking
they could have been unlocking	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I couldn't unlock
you couldn't unlock
he couldn't unlock
we couldn't unlock
you couldn't unlock
they couldn't unlock 	I couldn't be unlocking
you couldn't be unlocking
he couldn't be unlocking
we couldn't be unlocking
you couldn't be unlocking
they couldn't be unlocking	I couldn't have unlocked
you couldn't have unlocked
he couldn't have unlocked
we couldn't have unlocked
you couldn't have unlocked
they couldn't have unlocked	I couldn't have been unlocking
you couldn't have been unlocking
he couldn't have been unlocking
we couldn't have been unlocking
you couldn't have been unlocking
they couldn't have been unlocking	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I unlock?
could you unlock?
could he unlock?
could we unlock?
could you unlock?
could they unlock? 	could I be unlocking?
could you be unlocking?
could he be unlocking?
could we be unlocking?
could you be unlocking?
could they be unlocking? 	could I have unlocked?
could you have unlocked?
could he have unlocked?
could we have unlocked?
could you have unlocked?
could they have unlocked? 	could I have been unlocking?
could you have been unlocking?
could he have been unlocking?
could we have been unlocking?
could you have been unlocking?
could they have been unlocking? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
couldn't I unlock?
couldn't you unlock?
couldn't he unlock?
couldn't we unlock?
couldn't you unlock?
couldn't they unlock? 	couldn't I be unlocking?
couldn't you be unlocking?
couldn't he be unlocking?
couldn't we be unlocking?
couldn't you be unlocking?
couldn't they be unlocking? 	couldn't I have unlocked?
couldn't you have unlocked?
couldn't he have unlocked?
couldn't we have unlocked?
couldn't you have unlocked?
couldn't they have unlocked? 	couldn't I have been unlocking?
couldn't you have been unlocking?
couldn't he have been unlocking?
couldn't we have been unlocking?
couldn't you have been unlocking?
couldn't they have been unlocking?