must preascertain
Regular verb: preascertain - preascertained- preascertained

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I must preascertain
you must preascertain
she must preascertain
we must preascertain
you must preascertain
they must preascertain 	I must be preascertaining
you must be preascertaining
she must be preascertaining
we must be preascertaining
you must be preascertaining
they must be preascertaining	I must have preascertained
you must have preascertained
she 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
she must have been preascertaining
we must have been preascertaining
you must have been preascertaining
they must have been preascertaining	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I mustn't preascertain
you mustn't preascertain
she mustn't preascertain
we mustn't preascertain
you mustn't preascertain
they mustn't preascertain 	I mustn't be preascertaining
you mustn't be preascertaining
she mustn't be preascertaining
we mustn't be preascertaining
you mustn't be preascertaining
they mustn't be preascertaining	I mustn't have preascertained
you mustn't have preascertained
she mustn't have preascertained
we mustn't have preascertained
you mustn't have preascertained
they mustn't have preascertained	I mustn't have been preascertaining
you mustn't have been preascertaining
she mustn't have been preascertaining
we mustn't have been preascertaining
you mustn't have been preascertaining
they mustn't have been preascertaining	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
must I preascertain?
must you preascertain?
must she preascertain?
must we preascertain?
must you preascertain?
must they preascertain? 	must I be preascertaining?
must you be preascertaining?
must she be preascertaining?
must we be preascertaining?
must you be preascertaining?
must they be preascertaining? 	must I have preascertained?
must you have preascertained?
must she 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 she have been preascertaining?
must we have been preascertaining?
must you have been preascertaining?
must they have been preascertaining? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
mustn't I preascertain?
mustn't you preascertain?
mustn't she preascertain?
mustn't we preascertain?
mustn't you preascertain?
mustn't they preascertain? 	mustn't I be preascertaining?
mustn't you be preascertaining?
mustn't she be preascertaining?
mustn't we be preascertaining?
mustn't you be preascertaining?
mustn't they be preascertaining? 	mustn't I have preascertained?
mustn't you have preascertained?
mustn't she have preascertained?
mustn't we have preascertained?
mustn't you have preascertained?
mustn't they have preascertained? 	mustn't I have been preascertaining?
mustn't you have been preascertaining?
mustn't she have been preascertaining?
mustn't we have been preascertaining?
mustn't you have been preascertaining?
mustn't they have been preascertaining?