must fail
Verbo regular: fail - failed- failed

Afirmação 	
Forma simple 	Forma com V-ing 	Perfeito 	Perfeito com V-ing 	
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	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	

Negação 	
Forma simple 	Forma com V-ing 	Perfeito 	Perfeito com V-ing 	
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	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	

Forma interrogativa 	
Forma simple 	Forma com V-ing 	Perfeito 	Perfeito com V-ing 	
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? 	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? 	

Forma interro-Negação 	
Forma simple 	Forma com V-ing 	Perfeito 	Perfeito com V-ing 	
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? 	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?