I must frustrate you must frustrate he must frustrate we must frustrate you must frustrate they must frustrate
V-ing form
I must be frustrating you must be frustrating he must be frustrating we must be frustrating you must be frustrating they must be frustrating
Perfect
I must have frustrated you must have frustrated he must have frustrated we must have frustrated you must have frustrated they must have frustrated
V-ing perfect
I must have been frustrating you must have been frustrating he must have been frustrating we must have been frustrating you must have been frustrating they must have been frustrating
Negation
Simple form
I must not frustrate you must not frustrate he must not frustrate we must not frustrate you must not frustrate they must not frustrate
V-ing form
I must not be frustrating you must not be frustrating he must not be frustrating we must not be frustrating you must not be frustrating they must not be frustrating
Perfect
I must not have frustrated you must not have frustrated he must not have frustrated we must not have frustrated you must not have frustrated they must not have frustrated
V-ing perfect
I must not have been frustrating you must not have been frustrating he must not have been frustrating we must not have been frustrating you must not have been frustrating they must not have been frustrating
Interrogative form
Simple form
must I frustrate? must you frustrate? must he frustrate? must we frustrate? must you frustrate? must they frustrate?
V-ing form
must I be frustrating? must you be frustrating? must he be frustrating? must we be frustrating? must you be frustrating? must they be frustrating?
Perfect
must I have frustrated? must you have frustrated? must he have frustrated? must we have frustrated? must you have frustrated? must they have frustrated?
V-ing perfect
must I have been frustrating? must you have been frustrating? must he have been frustrating? must we have been frustrating? must you have been frustrating? must they have been frustrating?
Interro-negative form
Simple form
must I not frustrate? must you not frustrate? must he not frustrate? must we not frustrate? must you not frustrate? must they not frustrate?
V-ing form
must I not be frustrating? must you not be frustrating? must he not be frustrating? must we not be frustrating? must you not be frustrating? must they not be frustrating?
Perfect
must I not have frustrated? must you not have frustrated? must he not have frustrated? must we not have frustrated? must you not have frustrated? must they not have frustrated?
V-ing perfect
must I not have been frustrating? must you not have been frustrating? must he not have been frustrating? must we not have been frustrating? must you not have been frustrating? must they not have been frustrating?