must concentrate
Verbo regular: concentrate - concentrated- concentrated

Afirmación 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
I must concentrate
you must concentrate
he must concentrate
we must concentrate
you must concentrate
they must concentrate 	I must be concentrating
you must be concentrating
he must be concentrating
we must be concentrating
you must be concentrating
they must be concentrating	I must have concentrated
you must have concentrated
he must have concentrated
we must have concentrated
you must have concentrated
they must have concentrated	I must have been concentrating
you must have been concentrating
he must have been concentrating
we must have been concentrating
you must have been concentrating
they must have been concentrating	

Negación 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
I mustn't concentrate
you mustn't concentrate
he mustn't concentrate
we mustn't concentrate
you mustn't concentrate
they mustn't concentrate 	I mustn't be concentrating
you mustn't be concentrating
he mustn't be concentrating
we mustn't be concentrating
you mustn't be concentrating
they mustn't be concentrating	I mustn't have concentrated
you mustn't have concentrated
he mustn't have concentrated
we mustn't have concentrated
you mustn't have concentrated
they mustn't have concentrated	I mustn't have been concentrating
you mustn't have been concentrating
he mustn't have been concentrating
we mustn't have been concentrating
you mustn't have been concentrating
they mustn't have been concentrating	

Forma interrogativa 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
must I concentrate?
must you concentrate?
must he concentrate?
must we concentrate?
must you concentrate?
must they concentrate? 	must I be concentrating?
must you be concentrating?
must he be concentrating?
must we be concentrating?
must you be concentrating?
must they be concentrating? 	must I have concentrated?
must you have concentrated?
must he have concentrated?
must we have concentrated?
must you have concentrated?
must they have concentrated? 	must I have been concentrating?
must you have been concentrating?
must he have been concentrating?
must we have been concentrating?
must you have been concentrating?
must they have been concentrating? 	

Forma interro-negativa 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
mustn't I concentrate?
mustn't you concentrate?
mustn't he concentrate?
mustn't we concentrate?
mustn't you concentrate?
mustn't they concentrate? 	mustn't I be concentrating?
mustn't you be concentrating?
mustn't he be concentrating?
mustn't we be concentrating?
mustn't you be concentrating?
mustn't they be concentrating? 	mustn't I have concentrated?
mustn't you have concentrated?
mustn't he have concentrated?
mustn't we have concentrated?
mustn't you have concentrated?
mustn't they have concentrated? 	mustn't I have been concentrating?
mustn't you have been concentrating?
mustn't he have been concentrating?
mustn't we have been concentrating?
mustn't you have been concentrating?
mustn't they have been concentrating?