English verb conjugation
CAN CONCERN

Regular verb: concern - concerned - concerned

Affirmation

Simple form	V-ing form
I can concern you can concern she can concern we can concern you can concern they can concern	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	V-ing 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	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	V-ing form
I cannot concern you cannot concern she cannot concern we cannot concern you cannot concern they cannot concern	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	V-ing 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	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	V-ing form
can I concern? can you concern? can she concern? can we concern? can you concern? can they concern?	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	V-ing 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?	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	V-ing 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?	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	V-ing 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?	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?