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
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	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	

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

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

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