could unpin
Regular verb: unpin - unpinned- unpinned

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could unpin
you could unpin
he could unpin
we could unpin
you could unpin
they could unpin 	I could be unpinning
you could be unpinning
he could be unpinning
we could be unpinning
you could be unpinning
they could be unpinning	I could have unpinned
you could have unpinned
he could have unpinned
we could have unpinned
you could have unpinned
they could have unpinned	I could have been unpinning
you could have been unpinning
he could have been unpinning
we could have been unpinning
you could have been unpinning
they could have been unpinning	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I couldn't unpin
you couldn't unpin
he couldn't unpin
we couldn't unpin
you couldn't unpin
they couldn't unpin 	I couldn't be unpinning
you couldn't be unpinning
he couldn't be unpinning
we couldn't be unpinning
you couldn't be unpinning
they couldn't be unpinning	I couldn't have unpinned
you couldn't have unpinned
he couldn't have unpinned
we couldn't have unpinned
you couldn't have unpinned
they couldn't have unpinned	I couldn't have been unpinning
you couldn't have been unpinning
he couldn't have been unpinning
we couldn't have been unpinning
you couldn't have been unpinning
they couldn't have been unpinning	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I unpin?
could you unpin?
could he unpin?
could we unpin?
could you unpin?
could they unpin? 	could I be unpinning?
could you be unpinning?
could he be unpinning?
could we be unpinning?
could you be unpinning?
could they be unpinning? 	could I have unpinned?
could you have unpinned?
could he have unpinned?
could we have unpinned?
could you have unpinned?
could they have unpinned? 	could I have been unpinning?
could you have been unpinning?
could he have been unpinning?
could we have been unpinning?
could you have been unpinning?
could they have been unpinning? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
couldn't I unpin?
couldn't you unpin?
couldn't he unpin?
couldn't we unpin?
couldn't you unpin?
couldn't they unpin? 	couldn't I be unpinning?
couldn't you be unpinning?
couldn't he be unpinning?
couldn't we be unpinning?
couldn't you be unpinning?
couldn't they be unpinning? 	couldn't I have unpinned?
couldn't you have unpinned?
couldn't he have unpinned?
couldn't we have unpinned?
couldn't you have unpinned?
couldn't they have unpinned? 	couldn't I have been unpinning?
couldn't you have been unpinning?
couldn't he have been unpinning?
couldn't we have been unpinning?
couldn't you have been unpinning?
couldn't they have been unpinning?