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