English verb conjugation
MUST YACK

Regular verb: yack - yacked - yacked

Affirmation

Simple form	V-ing form
I must yack you must yack he must yack we must yack you must yack they must yack	I must be yacking you must be yacking he must be yacking we must be yacking you must be yacking they must be yacking
Perfect	V-ing perfect
I must have yacked you must have yacked he must have yacked we must have yacked you must have yacked they must have yacked	I must have been yacking you must have been yacking he must have been yacking we must have been yacking you must have been yacking they must have been yacking

Negation

Simple form	V-ing form
I must not yack you must not yack he must not yack we must not yack you must not yack they must not yack	I must not be yacking you must not be yacking he must not be yacking we must not be yacking you must not be yacking they must not be yacking
Perfect	V-ing perfect
I must not have yacked you must not have yacked he must not have yacked we must not have yacked you must not have yacked they must not have yacked	I must not have been yacking you must not have been yacking he must not have been yacking we must not have been yacking you must not have been yacking they must not have been yacking

Interrogative form

Simple form	V-ing form
must I yack? must you yack? must he yack? must we yack? must you yack? must they yack?	must I be yacking? must you be yacking? must he be yacking? must we be yacking? must you be yacking? must they be yacking?
Perfect	V-ing perfect
must I have yacked? must you have yacked? must he have yacked? must we have yacked? must you have yacked? must they have yacked?	must I have been yacking? must you have been yacking? must he have been yacking? must we have been yacking? must you have been yacking? must they have been yacking?

Interro-negative form

Simple form	V-ing form
must I not yack? must you not yack? must he not yack? must we not yack? must you not yack? must they not yack?	must I not be yacking? must you not be yacking? must he not be yacking? must we not be yacking? must you not be yacking? must they not be yacking?
Perfect	V-ing perfect
must I not have yacked? must you not have yacked? must he not have yacked? must we not have yacked? must you not have yacked? must they not have yacked?	must I not have been yacking? must you not have been yacking? must he not have been yacking? must we not have been yacking? must you not have been yacking? must they not have been yacking?