must concenter
Regular verb: concenter - concentered- concentered

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I must concenter
you must concenter
he must concenter
we must concenter
you must concenter
they must concenter 	I must be concentering
you must be concentering
he must be concentering
we must be concentering
you must be concentering
they must be concentering	I must have concentered
you must have concentered
he must have concentered
we must have concentered
you must have concentered
they must have concentered	I must have been concentering
you must have been concentering
he must have been concentering
we must have been concentering
you must have been concentering
they must have been concentering	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I mustn't concenter
you mustn't concenter
he mustn't concenter
we mustn't concenter
you mustn't concenter
they mustn't concenter 	I mustn't be concentering
you mustn't be concentering
he mustn't be concentering
we mustn't be concentering
you mustn't be concentering
they mustn't be concentering	I mustn't have concentered
you mustn't have concentered
he mustn't have concentered
we mustn't have concentered
you mustn't have concentered
they mustn't have concentered	I mustn't have been concentering
you mustn't have been concentering
he mustn't have been concentering
we mustn't have been concentering
you mustn't have been concentering
they mustn't have been concentering	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
must I concenter?
must you concenter?
must he concenter?
must we concenter?
must you concenter?
must they concenter? 	must I be concentering?
must you be concentering?
must he be concentering?
must we be concentering?
must you be concentering?
must they be concentering? 	must I have concentered?
must you have concentered?
must he have concentered?
must we have concentered?
must you have concentered?
must they have concentered? 	must I have been concentering?
must you have been concentering?
must he have been concentering?
must we have been concentering?
must you have been concentering?
must they have been concentering? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
mustn't I concenter?
mustn't you concenter?
mustn't he concenter?
mustn't we concenter?
mustn't you concenter?
mustn't they concenter? 	mustn't I be concentering?
mustn't you be concentering?
mustn't he be concentering?
mustn't we be concentering?
mustn't you be concentering?
mustn't they be concentering? 	mustn't I have concentered?
mustn't you have concentered?
mustn't he have concentered?
mustn't we have concentered?
mustn't you have concentered?
mustn't they have concentered? 	mustn't I have been concentering?
mustn't you have been concentering?
mustn't he have been concentering?
mustn't we have been concentering?
mustn't you have been concentering?
mustn't they have been concentering?