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