English verb conjugation
MUST UNDERTAIN

Regular verb: undertain - undertained - undertained

Affirmation

Simple form	V-ing form
I must undertain you must undertain she must undertain we must undertain you must undertain they must undertain	I must be undertaining you must be undertaining she must be undertaining we must be undertaining you must be undertaining they must be undertaining
Perfect	V-ing perfect
I must have undertained you must have undertained she must have undertained we must have undertained you must have undertained they must have undertained	I must have been undertaining you must have been undertaining she must have been undertaining we must have been undertaining you must have been undertaining they must have been undertaining

Negation

Simple form	V-ing form
I mustn't undertain you mustn't undertain she mustn't undertain we mustn't undertain you mustn't undertain they mustn't undertain	I mustn't be undertaining you mustn't be undertaining she mustn't be undertaining we mustn't be undertaining you mustn't be undertaining they mustn't be undertaining
Perfect	V-ing perfect
I mustn't have undertained you mustn't have undertained she mustn't have undertained we mustn't have undertained you mustn't have undertained they mustn't have undertained	I mustn't have been undertaining you mustn't have been undertaining she mustn't have been undertaining we mustn't have been undertaining you mustn't have been undertaining they mustn't have been undertaining

Interrogative form

Simple form	V-ing form
must I undertain? must you undertain? must she undertain? must we undertain? must you undertain? must they undertain?	must I be undertaining? must you be undertaining? must she be undertaining? must we be undertaining? must you be undertaining? must they be undertaining?
Perfect	V-ing perfect
must I have undertained? must you have undertained? must she have undertained? must we have undertained? must you have undertained? must they have undertained?	must I have been undertaining? must you have been undertaining? must she have been undertaining? must we have been undertaining? must you have been undertaining? must they have been undertaining?

Interro-negative form

Simple form	V-ing form
mustn't I undertain? mustn't you undertain? mustn't she undertain? mustn't we undertain? mustn't you undertain? mustn't they undertain?	mustn't I be undertaining? mustn't you be undertaining? mustn't she be undertaining? mustn't we be undertaining? mustn't you be undertaining? mustn't they be undertaining?
Perfect	V-ing perfect
mustn't I have undertained? mustn't you have undertained? mustn't she have undertained? mustn't we have undertained? mustn't you have undertained? mustn't they have undertained?	mustn't I have been undertaining? mustn't you have been undertaining? mustn't she have been undertaining? mustn't we have been undertaining? mustn't you have been undertaining? mustn't they have been undertaining?