English verb conjugation
MUST SIGN

Regular verb: sign - signed - signed

Affirmation

Simple form	V-ing form
I must sign you must sign she must sign we must sign you must sign they must sign	I must be signing you must be signing she must be signing we must be signing you must be signing they must be signing
Perfect	V-ing perfect
I must have signed you must have signed she must have signed we must have signed you must have signed they must have signed	I must have been signing you must have been signing she must have been signing we must have been signing you must have been signing they must have been signing

Negation

Simple form	V-ing form
I must not sign you must not sign she must not sign we must not sign you must not sign they must not sign	I must not be signing you must not be signing she must not be signing we must not be signing you must not be signing they must not be signing
Perfect	V-ing perfect
I must not have signed you must not have signed she must not have signed we must not have signed you must not have signed they must not have signed	I must not have been signing you must not have been signing she must not have been signing we must not have been signing you must not have been signing they must not have been signing

Interrogative form

Simple form	V-ing form
must I sign? must you sign? must she sign? must we sign? must you sign? must they sign?	must I be signing? must you be signing? must she be signing? must we be signing? must you be signing? must they be signing?
Perfect	V-ing perfect
must I have signed? must you have signed? must she have signed? must we have signed? must you have signed? must they have signed?	must I have been signing? must you have been signing? must she have been signing? must we have been signing? must you have been signing? must they have been signing?

Interro-negative form

Simple form	V-ing form
must I not sign? must you not sign? must she not sign? must we not sign? must you not sign? must they not sign?	must I not be signing? must you not be signing? must she not be signing? must we not be signing? must you not be signing? must they not be signing?
Perfect	V-ing perfect
must I not have signed? must you not have signed? must she not have signed? must we not have signed? must you not have signed? must they not have signed?	must I not have been signing? must you not have been signing? must she not have been signing? must we not have been signing? must you not have been signing? must they not have been signing?