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