I can preascertain you can preascertain she can preascertain we can preascertain you can preascertain they can preascertain
V-ing form
I can be preascertaining you can be preascertaining she can be preascertaining we can be preascertaining you can be preascertaining they can be preascertaining
Perfect
I can have preascertained you can have preascertained she can have preascertained we can have preascertained you can have preascertained they can have preascertained
V-ing perfect
I can have been preascertaining you can have been preascertaining she can have been preascertaining we can have been preascertaining you can have been preascertaining they can have been preascertaining
Negation
Simple form
I cannot preascertain you cannot preascertain she cannot preascertain we cannot preascertain you cannot preascertain they cannot preascertain
V-ing form
I cannot be preascertaining you cannot be preascertaining she cannot be preascertaining we cannot be preascertaining you cannot be preascertaining they cannot be preascertaining
Perfect
I cannot have preascertained you cannot have preascertained she cannot have preascertained we cannot have preascertained you cannot have preascertained they cannot have preascertained
V-ing perfect
I cannot have been preascertaining you cannot have been preascertaining she cannot have been preascertaining we cannot have been preascertaining you cannot have been preascertaining they cannot have been preascertaining
Interrogative form
Simple form
can I preascertain? can you preascertain? can she preascertain? can we preascertain? can you preascertain? can they preascertain?
V-ing form
can I be preascertaining? can you be preascertaining? can she be preascertaining? can we be preascertaining? can you be preascertaining? can they be preascertaining?
Perfect
can I have preascertained? can you have preascertained? can she have preascertained? can we have preascertained? can you have preascertained? can they have preascertained?
V-ing perfect
can I have been preascertaining? can you have been preascertaining? can she have been preascertaining? can we have been preascertaining? can you have been preascertaining? can they have been preascertaining?
Interro-negative form
Simple form
can I not preascertain? can you not preascertain? can she not preascertain? can we not preascertain? can you not preascertain? can they not preascertain?
V-ing form
can I not be preascertaining? can you not be preascertaining? can she not be preascertaining? can we not be preascertaining? can you not be preascertaining? can they not be preascertaining?
Perfect
can I not have preascertained? can you not have preascertained? can she not have preascertained? can we not have preascertained? can you not have preascertained? can they not have preascertained?
V-ing perfect
can I not have been preascertaining? can you not have been preascertaining? can she not have been preascertaining? can we not have been preascertaining? can you not have been preascertaining? can they not have been preascertaining?