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