can concern
Verbo regular: concern - concerned- concerned

Afirmación 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
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	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	

Negación 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
I can't concern
you can't concern
she 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
she can't be concerning
we can't be concerning
you can't be concerning
they can't be concerning	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	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	

Forma interrogativa 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
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? 	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? 	

Forma interro-negativa 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
can't I concern?
can't you concern?
can't she 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 she be concerning?
can't we be concerning?
can't you be concerning?
can't they be concerning? 	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? 	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?