I must undertake you must undertake she must undertake we must undertake you must undertake they must undertake
V-ing form
I must be undertaking you must be undertaking she must be undertaking we must be undertaking you must be undertaking they must be undertaking
Perfect
I must have undertaken you must have undertaken she must have undertaken we must have undertaken you must have undertaken they must have undertaken
V-ing perfect
I must have been undertaking you must have been undertaking she must have been undertaking we must have been undertaking you must have been undertaking they must have been undertaking
Negation
Simple form
I must not undertake you must not undertake she must not undertake we must not undertake you must not undertake they must not undertake
V-ing form
I must not be undertaking you must not be undertaking she must not be undertaking we must not be undertaking you must not be undertaking they must not be undertaking
Perfect
I must not have undertaken you must not have undertaken she must not have undertaken we must not have undertaken you must not have undertaken they must not have undertaken
V-ing perfect
I must not have been undertaking you must not have been undertaking she must not have been undertaking we must not have been undertaking you must not have been undertaking they must not have been undertaking
Interrogative form
Simple form
must I undertake? must you undertake? must she undertake? must we undertake? must you undertake? must they undertake?
V-ing form
must I be undertaking? must you be undertaking? must she be undertaking? must we be undertaking? must you be undertaking? must they be undertaking?
Perfect
must I have undertaken? must you have undertaken? must she have undertaken? must we have undertaken? must you have undertaken? must they have undertaken?
V-ing perfect
must I have been undertaking? must you have been undertaking? must she have been undertaking? must we have been undertaking? must you have been undertaking? must they have been undertaking?
Interro-negative form
Simple form
must I not undertake? must you not undertake? must she not undertake? must we not undertake? must you not undertake? must they not undertake?
V-ing form
must I not be undertaking? must you not be undertaking? must she not be undertaking? must we not be undertaking? must you not be undertaking? must they not be undertaking?
Perfect
must I not have undertaken? must you not have undertaken? must she not have undertaken? must we not have undertaken? must you not have undertaken? must they not have undertaken?
V-ing perfect
must I not have been undertaking? must you not have been undertaking? must she not have been undertaking? must we not have been undertaking? must you not have been undertaking? must they not have been undertaking?