must modify
Regular verb: modify - modified- modified

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I must modify
you must modify
he must modify
we must modify
you must modify
they must modify 	I must be modifying
you must be modifying
he must be modifying
we must be modifying
you must be modifying
they must be modifying	I must have modified
you must have modified
he must have modified
we must have modified
you must have modified
they must have modified	I must have been modifying
you must have been modifying
he must have been modifying
we must have been modifying
you must have been modifying
they must have been modifying	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I mustn't modify
you mustn't modify
he mustn't modify
we mustn't modify
you mustn't modify
they mustn't modify 	I mustn't be modifying
you mustn't be modifying
he mustn't be modifying
we mustn't be modifying
you mustn't be modifying
they mustn't be modifying	I mustn't have modified
you mustn't have modified
he mustn't have modified
we mustn't have modified
you mustn't have modified
they mustn't have modified	I mustn't have been modifying
you mustn't have been modifying
he mustn't have been modifying
we mustn't have been modifying
you mustn't have been modifying
they mustn't have been modifying	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
must I modify?
must you modify?
must he modify?
must we modify?
must you modify?
must they modify? 	must I be modifying?
must you be modifying?
must he be modifying?
must we be modifying?
must you be modifying?
must they be modifying? 	must I have modified?
must you have modified?
must he have modified?
must we have modified?
must you have modified?
must they have modified? 	must I have been modifying?
must you have been modifying?
must he have been modifying?
must we have been modifying?
must you have been modifying?
must they have been modifying? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
mustn't I modify?
mustn't you modify?
mustn't he modify?
mustn't we modify?
mustn't you modify?
mustn't they modify? 	mustn't I be modifying?
mustn't you be modifying?
mustn't he be modifying?
mustn't we be modifying?
mustn't you be modifying?
mustn't they be modifying? 	mustn't I have modified?
mustn't you have modified?
mustn't he have modified?
mustn't we have modified?
mustn't you have modified?
mustn't they have modified? 	mustn't I have been modifying?
mustn't you have been modifying?
mustn't he have been modifying?
mustn't we have been modifying?
mustn't you have been modifying?
mustn't they have been modifying?