I must concern you must concern she must concern we must concern you must concern they must concern
V-ing form
I must be concerning you must be concerning she must be concerning we must be concerning you must be concerning they must be concerning
Perfect
I must have concerned you must have concerned she must have concerned we must have concerned you must have concerned they must have concerned
V-ing perfect
I must have been concerning you must have been concerning she must have been concerning we must have been concerning you must have been concerning they must have been concerning
Negation
Simple form
I must not concern you must not concern she must not concern we must not concern you must not concern they must not concern
V-ing form
I must not be concerning you must not be concerning she must not be concerning we must not be concerning you must not be concerning they must not be concerning
Perfect
I must not have concerned you must not have concerned she must not have concerned we must not have concerned you must not have concerned they must not have concerned
V-ing perfect
I must not have been concerning you must not have been concerning she must not have been concerning we must not have been concerning you must not have been concerning they must not have been concerning
Interrogative form
Simple form
must I concern? must you concern? must she concern? must we concern? must you concern? must they concern?
V-ing form
must I be concerning? must you be concerning? must she be concerning? must we be concerning? must you be concerning? must they be concerning?
Perfect
must I have concerned? must you have concerned? must she have concerned? must we have concerned? must you have concerned? must they have concerned?
V-ing perfect
must I have been concerning? must you have been concerning? must she have been concerning? must we have been concerning? must you have been concerning? must they have been concerning?
Interro-negative form
Simple form
must I not concern? must you not concern? must she not concern? must we not concern? must you not concern? must they not concern?
V-ing form
must I not be concerning? must you not be concerning? must she not be concerning? must we not be concerning? must you not be concerning? must they not be concerning?
Perfect
must I not have concerned? must you not have concerned? must she not have concerned? must we not have concerned? must you not have concerned? must they not have concerned?
V-ing perfect
must I not have been concerning? must you not have been concerning? must she not have been concerning? must we not have been concerning? must you not have been concerning? must they not have been concerning?