must clench
Regular verb: clench - clenched- clenched

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I must clench
you must clench
he must clench
we must clench
you must clench
they must clench 	I must be clenching
you must be clenching
he must be clenching
we must be clenching
you must be clenching
they must be clenching	I must have clenched
you must have clenched
he must have clenched
we must have clenched
you must have clenched
they must have clenched	I must have been clenching
you must have been clenching
he must have been clenching
we must have been clenching
you must have been clenching
they must have been clenching	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I mustn't clench
you mustn't clench
he mustn't clench
we mustn't clench
you mustn't clench
they mustn't clench 	I mustn't be clenching
you mustn't be clenching
he mustn't be clenching
we mustn't be clenching
you mustn't be clenching
they mustn't be clenching	I mustn't have clenched
you mustn't have clenched
he mustn't have clenched
we mustn't have clenched
you mustn't have clenched
they mustn't have clenched	I mustn't have been clenching
you mustn't have been clenching
he mustn't have been clenching
we mustn't have been clenching
you mustn't have been clenching
they mustn't have been clenching	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
must I clench?
must you clench?
must he clench?
must we clench?
must you clench?
must they clench? 	must I be clenching?
must you be clenching?
must he be clenching?
must we be clenching?
must you be clenching?
must they be clenching? 	must I have clenched?
must you have clenched?
must he have clenched?
must we have clenched?
must you have clenched?
must they have clenched? 	must I have been clenching?
must you have been clenching?
must he have been clenching?
must we have been clenching?
must you have been clenching?
must they have been clenching? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
mustn't I clench?
mustn't you clench?
mustn't he clench?
mustn't we clench?
mustn't you clench?
mustn't they clench? 	mustn't I be clenching?
mustn't you be clenching?
mustn't he be clenching?
mustn't we be clenching?
mustn't you be clenching?
mustn't they be clenching? 	mustn't I have clenched?
mustn't you have clenched?
mustn't he have clenched?
mustn't we have clenched?
mustn't you have clenched?
mustn't they have clenched? 	mustn't I have been clenching?
mustn't you have been clenching?
mustn't he have been clenching?
mustn't we have been clenching?
mustn't you have been clenching?
mustn't they have been clenching?