English verb conjugation
MUST LACK

Regular verb: lack - lacked - lacked

Affirmation

Simple form	V-ing form
I must lack you must lack he must lack we must lack you must lack they must lack	I must be lacking you must be lacking he must be lacking we must be lacking you must be lacking they must be lacking
Perfect	V-ing perfect
I must have lacked you must have lacked he must have lacked we must have lacked you must have lacked they must have lacked	I must have been lacking you must have been lacking he must have been lacking we must have been lacking you must have been lacking they must have been lacking

Negation

Simple form	V-ing form
I must not lack you must not lack he must not lack we must not lack you must not lack they must not lack	I must not be lacking you must not be lacking he must not be lacking we must not be lacking you must not be lacking they must not be lacking
Perfect	V-ing perfect
I must not have lacked you must not have lacked he must not have lacked we must not have lacked you must not have lacked they must not have lacked	I must not have been lacking you must not have been lacking he must not have been lacking we must not have been lacking you must not have been lacking they must not have been lacking

Interrogative form

Simple form	V-ing form
must I lack? must you lack? must he lack? must we lack? must you lack? must they lack?	must I be lacking? must you be lacking? must he be lacking? must we be lacking? must you be lacking? must they be lacking?
Perfect	V-ing perfect
must I have lacked? must you have lacked? must he have lacked? must we have lacked? must you have lacked? must they have lacked?	must I have been lacking? must you have been lacking? must he have been lacking? must we have been lacking? must you have been lacking? must they have been lacking?

Interro-negative form

Simple form	V-ing form
must I not lack? must you not lack? must he not lack? must we not lack? must you not lack? must they not lack?	must I not be lacking? must you not be lacking? must he not be lacking? must we not be lacking? must you not be lacking? must they not be lacking?
Perfect	V-ing perfect
must I not have lacked? must you not have lacked? must he not have lacked? must we not have lacked? must you not have lacked? must they not have lacked?	must I not have been lacking? must you not have been lacking? must he not have been lacking? must we not have been lacking? must you not have been lacking? must they not have been lacking?