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
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	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	

Negación 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
I cannot concern
you cannot concern
he cannot concern
we cannot concern
you cannot concern
they cannot concern 	I cannot be concerning
you cannot be concerning
he cannot be concerning
we cannot be concerning
you cannot be concerning
they cannot be concerning	I cannot have concerned
you cannot have concerned
he 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
he cannot have been concerning
we cannot have been concerning
you cannot have been concerning
they cannot have been concerning	

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

Forma interro-negativa 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
can I not concern?
can you not concern?
can he 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 he not be concerning?
can we not be concerning?
can you not be concerning?
can they not be concerning? 	can I not have concerned?
can you not have concerned?
can he 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 he not have been concerning?
can we not have been concerning?
can you not have been concerning?
can they not have been concerning?