English verb conjugation
MUST FAIL

Regular verb: fail - failed - failed

Affirmation

Simple form	V-ing form
I must fail you must fail he must fail we must fail you must fail they must fail	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	V-ing 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	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	V-ing 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	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	V-ing 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	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	V-ing form
must I fail? must you fail? must he fail? must we fail? must you fail? must they fail?	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	V-ing 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?	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	V-ing 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?	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	V-ing 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?	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?