must preascertain
Verbo regular: preascertain - preascertained- preascertained

Afirmación 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
I must preascertain
you must preascertain
he must preascertain
we must preascertain
you must preascertain
they must preascertain 	I must be preascertaining
you must be preascertaining
he must be preascertaining
we must be preascertaining
you must be preascertaining
they must be preascertaining	I must have preascertained
you must have preascertained
he must have preascertained
we must have preascertained
you must have preascertained
they must have preascertained	I must have been preascertaining
you must have been preascertaining
he must have been preascertaining
we must have been preascertaining
you must have been preascertaining
they must have been preascertaining	

Negación 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
I must not preascertain
you must not preascertain
he must not preascertain
we must not preascertain
you must not preascertain
they must not preascertain 	I must not be preascertaining
you must not be preascertaining
he must not be preascertaining
we must not be preascertaining
you must not be preascertaining
they must not be preascertaining	I must not have preascertained
you must not have preascertained
he must not have preascertained
we must not have preascertained
you must not have preascertained
they must not have preascertained	I must not have been preascertaining
you must not have been preascertaining
he must not have been preascertaining
we must not have been preascertaining
you must not have been preascertaining
they must not have been preascertaining	

Forma interrogativa 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
must I preascertain?
must you preascertain?
must he preascertain?
must we preascertain?
must you preascertain?
must they preascertain? 	must I be preascertaining?
must you be preascertaining?
must he be preascertaining?
must we be preascertaining?
must you be preascertaining?
must they be preascertaining? 	must I have preascertained?
must you have preascertained?
must he have preascertained?
must we have preascertained?
must you have preascertained?
must they have preascertained? 	must I have been preascertaining?
must you have been preascertaining?
must he have been preascertaining?
must we have been preascertaining?
must you have been preascertaining?
must they have been preascertaining? 	

Forma interro-negativa 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
must I not preascertain?
must you not preascertain?
must he not preascertain?
must we not preascertain?
must you not preascertain?
must they not preascertain? 	must I not be preascertaining?
must you not be preascertaining?
must he not be preascertaining?
must we not be preascertaining?
must you not be preascertaining?
must they not be preascertaining? 	must I not have preascertained?
must you not have preascertained?
must he not have preascertained?
must we not have preascertained?
must you not have preascertained?
must they not have preascertained? 	must I not have been preascertaining?
must you not have been preascertaining?
must he not have been preascertaining?
must we not have been preascertaining?
must you not have been preascertaining?
must they not have been preascertaining?