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