could distinguish
Regular verb: distinguish - distinguished- distinguished

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could distinguish
you could distinguish
he could distinguish
we could distinguish
you could distinguish
they could distinguish 	I could be distinguishing
you could be distinguishing
he could be distinguishing
we could be distinguishing
you could be distinguishing
they could be distinguishing	I could have distinguished
you could have distinguished
he could have distinguished
we could have distinguished
you could have distinguished
they could have distinguished	I could have been distinguishing
you could have been distinguishing
he could have been distinguishing
we could have been distinguishing
you could have been distinguishing
they could have been distinguishing	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I couldn't distinguish
you couldn't distinguish
he couldn't distinguish
we couldn't distinguish
you couldn't distinguish
they couldn't distinguish 	I couldn't be distinguishing
you couldn't be distinguishing
he couldn't be distinguishing
we couldn't be distinguishing
you couldn't be distinguishing
they couldn't be distinguishing	I couldn't have distinguished
you couldn't have distinguished
he couldn't have distinguished
we couldn't have distinguished
you couldn't have distinguished
they couldn't have distinguished	I couldn't have been distinguishing
you couldn't have been distinguishing
he couldn't have been distinguishing
we couldn't have been distinguishing
you couldn't have been distinguishing
they couldn't have been distinguishing	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I distinguish?
could you distinguish?
could he distinguish?
could we distinguish?
could you distinguish?
could they distinguish? 	could I be distinguishing?
could you be distinguishing?
could he be distinguishing?
could we be distinguishing?
could you be distinguishing?
could they be distinguishing? 	could I have distinguished?
could you have distinguished?
could he have distinguished?
could we have distinguished?
could you have distinguished?
could they have distinguished? 	could I have been distinguishing?
could you have been distinguishing?
could he have been distinguishing?
could we have been distinguishing?
could you have been distinguishing?
could they have been distinguishing? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
couldn't I distinguish?
couldn't you distinguish?
couldn't he distinguish?
couldn't we distinguish?
couldn't you distinguish?
couldn't they distinguish? 	couldn't I be distinguishing?
couldn't you be distinguishing?
couldn't he be distinguishing?
couldn't we be distinguishing?
couldn't you be distinguishing?
couldn't they be distinguishing? 	couldn't I have distinguished?
couldn't you have distinguished?
couldn't he have distinguished?
couldn't we have distinguished?
couldn't you have distinguished?
couldn't they have distinguished? 	couldn't I have been distinguishing?
couldn't you have been distinguishing?
couldn't he have been distinguishing?
couldn't we have been distinguishing?
couldn't you have been distinguishing?
couldn't they have been distinguishing?