English verb conjugation
MUST VARY

Regular verb: vary - varied - varied

Affirmation

Simple form	V-ing form
I must vary you must vary he must vary we must vary you must vary they must vary	I must be varying you must be varying he must be varying we must be varying you must be varying they must be varying
Perfect	V-ing perfect
I must have varied you must have varied he must have varied we must have varied you must have varied they must have varied	I must have been varying you must have been varying he must have been varying we must have been varying you must have been varying they must have been varying

Negation

Simple form	V-ing form
I must not vary you must not vary he must not vary we must not vary you must not vary they must not vary	I must not be varying you must not be varying he must not be varying we must not be varying you must not be varying they must not be varying
Perfect	V-ing perfect
I must not have varied you must not have varied he must not have varied we must not have varied you must not have varied they must not have varied	I must not have been varying you must not have been varying he must not have been varying we must not have been varying you must not have been varying they must not have been varying

Interrogative form

Simple form	V-ing form
must I vary? must you vary? must he vary? must we vary? must you vary? must they vary?	must I be varying? must you be varying? must he be varying? must we be varying? must you be varying? must they be varying?
Perfect	V-ing perfect
must I have varied? must you have varied? must he have varied? must we have varied? must you have varied? must they have varied?	must I have been varying? must you have been varying? must he have been varying? must we have been varying? must you have been varying? must they have been varying?

Interro-negative form

Simple form	V-ing form
must I not vary? must you not vary? must he not vary? must we not vary? must you not vary? must they not vary?	must I not be varying? must you not be varying? must he not be varying? must we not be varying? must you not be varying? must they not be varying?
Perfect	V-ing perfect
must I not have varied? must you not have varied? must he not have varied? must we not have varied? must you not have varied? must they not have varied?	must I not have been varying? must you not have been varying? must he not have been varying? must we not have been varying? must you not have been varying? must they not have been varying?