I must untwist you must untwist he must untwist we must untwist you must untwist they must untwist
V-ing form
I must be untwisting you must be untwisting he must be untwisting we must be untwisting you must be untwisting they must be untwisting
Perfect
I must have untwisted you must have untwisted he must have untwisted we must have untwisted you must have untwisted they must have untwisted
V-ing perfect
I must have been untwisting you must have been untwisting he must have been untwisting we must have been untwisting you must have been untwisting they must have been untwisting
Negation
Simple form
I mustn't untwist you mustn't untwist he mustn't untwist we mustn't untwist you mustn't untwist they mustn't untwist
V-ing form
I mustn't be untwisting you mustn't be untwisting he mustn't be untwisting we mustn't be untwisting you mustn't be untwisting they mustn't be untwisting
Perfect
I mustn't have untwisted you mustn't have untwisted he mustn't have untwisted we mustn't have untwisted you mustn't have untwisted they mustn't have untwisted
V-ing perfect
I mustn't have been untwisting you mustn't have been untwisting he mustn't have been untwisting we mustn't have been untwisting you mustn't have been untwisting they mustn't have been untwisting
Interrogative form
Simple form
must I untwist? must you untwist? must he untwist? must we untwist? must you untwist? must they untwist?
V-ing form
must I be untwisting? must you be untwisting? must he be untwisting? must we be untwisting? must you be untwisting? must they be untwisting?
Perfect
must I have untwisted? must you have untwisted? must he have untwisted? must we have untwisted? must you have untwisted? must they have untwisted?
V-ing perfect
must I have been untwisting? must you have been untwisting? must he have been untwisting? must we have been untwisting? must you have been untwisting? must they have been untwisting?
Interro-negative form
Simple form
mustn't I untwist? mustn't you untwist? mustn't he untwist? mustn't we untwist? mustn't you untwist? mustn't they untwist?
V-ing form
mustn't I be untwisting? mustn't you be untwisting? mustn't he be untwisting? mustn't we be untwisting? mustn't you be untwisting? mustn't they be untwisting?
Perfect
mustn't I have untwisted? mustn't you have untwisted? mustn't he have untwisted? mustn't we have untwisted? mustn't you have untwisted? mustn't they have untwisted?
V-ing perfect
mustn't I have been untwisting? mustn't you have been untwisting? mustn't he have been untwisting? mustn't we have been untwisting? mustn't you have been untwisting? mustn't they have been untwisting?