English verb conjugation
MUST RETAIN

Regular verb: retain - retained - retained

Affirmation

Simple form	V-ing form
I must retain you must retain she must retain we must retain you must retain they must retain	I must be retaining you must be retaining she must be retaining we must be retaining you must be retaining they must be retaining
Perfect	V-ing perfect
I must have retained you must have retained she must have retained we must have retained you must have retained they must have retained	I must have been retaining you must have been retaining she must have been retaining we must have been retaining you must have been retaining they must have been retaining

Negation

Simple form	V-ing form
I must not retain you must not retain she must not retain we must not retain you must not retain they must not retain	I must not be retaining you must not be retaining she must not be retaining we must not be retaining you must not be retaining they must not be retaining
Perfect	V-ing perfect
I must not have retained you must not have retained she must not have retained we must not have retained you must not have retained they must not have retained	I must not have been retaining you must not have been retaining she must not have been retaining we must not have been retaining you must not have been retaining they must not have been retaining

Interrogative form

Simple form	V-ing form
must I retain? must you retain? must she retain? must we retain? must you retain? must they retain?	must I be retaining? must you be retaining? must she be retaining? must we be retaining? must you be retaining? must they be retaining?
Perfect	V-ing perfect
must I have retained? must you have retained? must she have retained? must we have retained? must you have retained? must they have retained?	must I have been retaining? must you have been retaining? must she have been retaining? must we have been retaining? must you have been retaining? must they have been retaining?

Interro-negative form

Simple form	V-ing form
must I not retain? must you not retain? must she not retain? must we not retain? must you not retain? must they not retain?	must I not be retaining? must you not be retaining? must she not be retaining? must we not be retaining? must you not be retaining? must they not be retaining?
Perfect	V-ing perfect
must I not have retained? must you not have retained? must she not have retained? must we not have retained? must you not have retained? must they not have retained?	must I not have been retaining? must you not have been retaining? must she not have been retaining? must we not have been retaining? must you not have been retaining? must they not have been retaining?