English verb conjugation
CAN CONCERN

Regular verb: concern - concerned - concerned

Affirmation

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