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 must not preascertain
you must not preascertain
she 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
she 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
she 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
she must not have been preascertaining
we must not have been preascertaining
you must not have been preascertaining
they must not 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 	
must I not preascertain?
must you not preascertain?
must she 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 she 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 she 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 she not have been preascertaining?
must we not have been preascertaining?
must you not have been preascertaining?
must they not have been preascertaining?