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 cannot concern you cannot concern she cannot concern we cannot concern you cannot concern they cannot concern
V-ing form
I cannot be concerning you cannot be concerning she cannot be concerning we cannot be concerning you cannot be concerning they cannot be concerning
Perfect
I cannot have concerned you cannot have concerned she cannot have concerned we cannot have concerned you cannot have concerned they cannot have concerned
V-ing perfect
I cannot have been concerning you cannot have been concerning she cannot have been concerning we cannot have been concerning you cannot have been concerning they cannot 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 I not concern? can you not concern? can she not concern? can we not concern? can you not concern? can they not concern?
V-ing form
can I not be concerning? can you not be concerning? can she not be concerning? can we not be concerning? can you not be concerning? can they not be concerning?
Perfect
can I not have concerned? can you not have concerned? can she not have concerned? can we not have concerned? can you not have concerned? can they not have concerned?
V-ing perfect
can I not have been concerning? can you not have been concerning? can she not have been concerning? can we not have been concerning? can you not have been concerning? can they not have been concerning?