English verb conjugation
COULD DISTINGUISH

Regular verb: distinguish - distinguished - distinguished

Affirmation

Simple form	V-ing form
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
Perfect	V-ing perfect
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
I could not distinguish you could not distinguish he could not distinguish we could not distinguish you could not distinguish they could not distinguish	I could not be distinguishing you could not be distinguishing he could not be distinguishing we could not be distinguishing you could not be distinguishing they could not be distinguishing
Perfect	V-ing perfect
I could not have distinguished you could not have distinguished he could not have distinguished we could not have distinguished you could not have distinguished they could not have distinguished	I could not have been distinguishing you could not have been distinguishing he could not have been distinguishing we could not have been distinguishing you could not have been distinguishing they could not have been distinguishing

Interrogative form

Simple form	V-ing form
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?
Perfect	V-ing perfect
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
could I not distinguish? could you not distinguish? could he not distinguish? could we not distinguish? could you not distinguish? could they not distinguish?	could I not be distinguishing? could you not be distinguishing? could he not be distinguishing? could we not be distinguishing? could you not be distinguishing? could they not be distinguishing?
Perfect	V-ing perfect
could I not have distinguished? could you not have distinguished? could he not have distinguished? could we not have distinguished? could you not have distinguished? could they not have distinguished?	could I not have been distinguishing? could you not have been distinguishing? could he not have been distinguishing? could we not have been distinguishing? could you not have been distinguishing? could they not have been distinguishing?