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 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
Perfect	V-ing perfect
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
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
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?
Perfect	V-ing perfect
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?