English verb conjugation
COULD ASCERTAIN

Regular verb: ascertain - ascertained - ascertained

Affirmation

Simple form	V-ing form
I could ascertain you could ascertain he could ascertain we could ascertain you could ascertain they could ascertain	I could be ascertaining you could be ascertaining he could be ascertaining we could be ascertaining you could be ascertaining they could be ascertaining
Perfect	V-ing perfect
I could have ascertained you could have ascertained he could have ascertained we could have ascertained you could have ascertained they could have ascertained	I could have been ascertaining you could have been ascertaining he could have been ascertaining we could have been ascertaining you could have been ascertaining they could have been ascertaining

Negation

Simple form	V-ing form
I couldn't ascertain you couldn't ascertain he couldn't ascertain we couldn't ascertain you couldn't ascertain they couldn't ascertain	I couldn't be ascertaining you couldn't be ascertaining he couldn't be ascertaining we couldn't be ascertaining you couldn't be ascertaining they couldn't be ascertaining
Perfect	V-ing perfect
I couldn't have ascertained you couldn't have ascertained he couldn't have ascertained we couldn't have ascertained you couldn't have ascertained they couldn't have ascertained	I couldn't have been ascertaining you couldn't have been ascertaining he couldn't have been ascertaining we couldn't have been ascertaining you couldn't have been ascertaining they couldn't have been ascertaining

Interrogative form

Simple form	V-ing form
could I ascertain? could you ascertain? could he ascertain? could we ascertain? could you ascertain? could they ascertain?	could I be ascertaining? could you be ascertaining? could he be ascertaining? could we be ascertaining? could you be ascertaining? could they be ascertaining?
Perfect	V-ing perfect
could I have ascertained? could you have ascertained? could he have ascertained? could we have ascertained? could you have ascertained? could they have ascertained?	could I have been ascertaining? could you have been ascertaining? could he have been ascertaining? could we have been ascertaining? could you have been ascertaining? could they have been ascertaining?

Interro-negative form

Simple form	V-ing form
couldn't I ascertain? couldn't you ascertain? couldn't he ascertain? couldn't we ascertain? couldn't you ascertain? couldn't they ascertain?	couldn't I be ascertaining? couldn't you be ascertaining? couldn't he be ascertaining? couldn't we be ascertaining? couldn't you be ascertaining? couldn't they be ascertaining?
Perfect	V-ing perfect
couldn't I have ascertained? couldn't you have ascertained? couldn't he have ascertained? couldn't we have ascertained? couldn't you have ascertained? couldn't they have ascertained?	couldn't I have been ascertaining? couldn't you have been ascertaining? couldn't he have been ascertaining? couldn't we have been ascertaining? couldn't you have been ascertaining? couldn't they have been ascertaining?