English verb conjugation
MUST ASCERTAIN

Regular verb: ascertain - ascertained - ascertained

Affirmation

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

Negation

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

Interrogative form

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

Interro-negative form

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