English verb conjugation
MUST CONCERN

Regular verb: concern - concerned - concerned

Affirmation

Simple form	V-ing form
I must concern you must concern he must concern we must concern you must concern they must concern	I must be concerning you must be concerning he must be concerning we must be concerning you must be concerning they must be concerning
Perfect	V-ing perfect
I must have concerned you must have concerned he must have concerned we must have concerned you must have concerned they must have concerned	I must have been concerning you must have been concerning he must have been concerning we must have been concerning you must have been concerning they must have been concerning

Negation

Simple form	V-ing form
I mustn't concern you mustn't concern he mustn't concern we mustn't concern you mustn't concern they mustn't concern	I mustn't be concerning you mustn't be concerning he mustn't be concerning we mustn't be concerning you mustn't be concerning they mustn't be concerning
Perfect	V-ing perfect
I mustn't have concerned you mustn't have concerned he mustn't have concerned we mustn't have concerned you mustn't have concerned they mustn't have concerned	I mustn't have been concerning you mustn't have been concerning he mustn't have been concerning we mustn't have been concerning you mustn't have been concerning they mustn't have been concerning

Interrogative form

Simple form	V-ing form
must I concern? must you concern? must he concern? must we concern? must you concern? must they concern?	must I be concerning? must you be concerning? must he be concerning? must we be concerning? must you be concerning? must they be concerning?
Perfect	V-ing perfect
must I have concerned? must you have concerned? must he have concerned? must we have concerned? must you have concerned? must they have concerned?	must I have been concerning? must you have been concerning? must he have been concerning? must we have been concerning? must you have been concerning? must they have been concerning?

Interro-negative form

Simple form	V-ing form
mustn't I concern? mustn't you concern? mustn't he concern? mustn't we concern? mustn't you concern? mustn't they concern?	mustn't I be concerning? mustn't you be concerning? mustn't he be concerning? mustn't we be concerning? mustn't you be concerning? mustn't they be concerning?
Perfect	V-ing perfect
mustn't I have concerned? mustn't you have concerned? mustn't he have concerned? mustn't we have concerned? mustn't you have concerned? mustn't they have concerned?	mustn't I have been concerning? mustn't you have been concerning? mustn't he have been concerning? mustn't we have been concerning? mustn't you have been concerning? mustn't they have been concerning?