[Sono paati-e-wa [Hanako-ga ________ itta-daroo-ka] [Jiro-ga ________ itta-daroo-ka]] (watashi-ni-wa wakara-nai).
the party-to-TOP Hanako-NOM  went-may.well.be-KA Jiro-NOM  went-may.well.be-KA I-DAT-TOP know-NEG
I don’t know which is true: Hanako may well have gone to the party or Jiro may well have gone to the party.