I must fail you must fail he must fail we must fail you must fail they must fail
V-ing form
I must be failing you must be failing he must be failing we must be failing you must be failing they must be failing
Perfect
I must have failed you must have failed he must have failed we must have failed you must have failed they must have failed
V-ing perfect
I must have been failing you must have been failing he must have been failing we must have been failing you must have been failing they must have been failing
Negation
Simple form
I must not fail you must not fail he must not fail we must not fail you must not fail they must not fail
V-ing form
I must not be failing you must not be failing he must not be failing we must not be failing you must not be failing they must not be failing
Perfect
I must not have failed you must not have failed he must not have failed we must not have failed you must not have failed they must not have failed
V-ing perfect
I must not have been failing you must not have been failing he must not have been failing we must not have been failing you must not have been failing they must not have been failing
Interrogative form
Simple form
must I fail? must you fail? must he fail? must we fail? must you fail? must they fail?
V-ing form
must I be failing? must you be failing? must he be failing? must we be failing? must you be failing? must they be failing?
Perfect
must I have failed? must you have failed? must he have failed? must we have failed? must you have failed? must they have failed?
V-ing perfect
must I have been failing? must you have been failing? must he have been failing? must we have been failing? must you have been failing? must they have been failing?
Interro-negative form
Simple form
must I not fail? must you not fail? must he not fail? must we not fail? must you not fail? must they not fail?
V-ing form
must I not be failing? must you not be failing? must he not be failing? must we not be failing? must you not be failing? must they not be failing?
Perfect
must I not have failed? must you not have failed? must he not have failed? must we not have failed? must you not have failed? must they not have failed?
V-ing perfect
must I not have been failing? must you not have been failing? must he not have been failing? must we not have been failing? must you not have been failing? must they not have been failing?