English verb conjugation
MUST FAIL

Regular verb: fail - failed - failed

Affirmation

Simple form	V-ing form
I must fail you must fail she must fail we must fail you must fail they must fail	I must be failing you must be failing she 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 she 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 she 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 mustn't fail you mustn't fail she mustn't fail we mustn't fail you mustn't fail they mustn't fail	I mustn't be failing you mustn't be failing she mustn't be failing we mustn't be failing you mustn't be failing they mustn't be failing
Perfect	V-ing perfect
I mustn't have failed you mustn't have failed she mustn't have failed we mustn't have failed you mustn't have failed they mustn't have failed	I mustn't have been failing you mustn't have been failing she mustn't have been failing we mustn't have been failing you mustn't have been failing they mustn't have been failing

Interrogative form

Simple form	V-ing form
must I fail? must you fail? must she fail? must we fail? must you fail? must they fail?	must I be failing? must you be failing? must she 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 she 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 she 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
mustn't I fail? mustn't you fail? mustn't she fail? mustn't we fail? mustn't you fail? mustn't they fail?	mustn't I be failing? mustn't you be failing? mustn't she be failing? mustn't we be failing? mustn't you be failing? mustn't they be failing?
Perfect	V-ing perfect
mustn't I have failed? mustn't you have failed? mustn't she have failed? mustn't we have failed? mustn't you have failed? mustn't they have failed?	mustn't I have been failing? mustn't you have been failing? mustn't she have been failing? mustn't we have been failing? mustn't you have been failing? mustn't they have been failing?