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