must ascertain
Verbo regular: ascertain - ascertained- ascertained

Afirmação 	
Forma simple 	Forma com V-ing 	Perfeito 	Perfeito com V-ing 	
I must ascertain
you must ascertain
she must ascertain
we must ascertain
you must ascertain
they must ascertain 	I must be ascertaining
you must be ascertaining
she must be ascertaining
we must be ascertaining
you must be ascertaining
they must be ascertaining	I must have ascertained
you must have ascertained
she must have ascertained
we must have ascertained
you must have ascertained
they must have ascertained	I must have been ascertaining
you must have been ascertaining
she must have been ascertaining
we must have been ascertaining
you must have been ascertaining
they must have been ascertaining	

Negação 	
Forma simple 	Forma com V-ing 	Perfeito 	Perfeito com V-ing 	
I must not ascertain
you must not ascertain
she must not ascertain
we must not ascertain
you must not ascertain
they must not ascertain 	I must not be ascertaining
you must not be ascertaining
she must not be ascertaining
we must not be ascertaining
you must not be ascertaining
they must not be ascertaining	I must not have ascertained
you must not have ascertained
she must not have ascertained
we must not have ascertained
you must not have ascertained
they must not have ascertained	I must not have been ascertaining
you must not have been ascertaining
she must not have been ascertaining
we must not have been ascertaining
you must not have been ascertaining
they must not have been ascertaining	

Forma interrogativa 	
Forma simple 	Forma com V-ing 	Perfeito 	Perfeito com V-ing 	
must I ascertain?
must you ascertain?
must she ascertain?
must we ascertain?
must you ascertain?
must they ascertain? 	must I be ascertaining?
must you be ascertaining?
must she be ascertaining?
must we be ascertaining?
must you be ascertaining?
must they be ascertaining? 	must I have ascertained?
must you have ascertained?
must she have ascertained?
must we have ascertained?
must you have ascertained?
must they have ascertained? 	must I have been ascertaining?
must you have been ascertaining?
must she have been ascertaining?
must we have been ascertaining?
must you have been ascertaining?
must they have been ascertaining? 	

Forma interro-Negação 	
Forma simple 	Forma com V-ing 	Perfeito 	Perfeito com V-ing 	
must I not ascertain?
must you not ascertain?
must she not ascertain?
must we not ascertain?
must you not ascertain?
must they not ascertain? 	must I not be ascertaining?
must you not be ascertaining?
must she not be ascertaining?
must we not be ascertaining?
must you not be ascertaining?
must they not be ascertaining? 	must I not have ascertained?
must you not have ascertained?
must she not have ascertained?
must we not have ascertained?
must you not have ascertained?
must they not have ascertained? 	must I not have been ascertaining?
must you not have been ascertaining?
must she not have been ascertaining?
must we not have been ascertaining?
must you not have been ascertaining?
must they not have been ascertaining?