Answer: C-3PO
At the beginning of the movie, C-3PO spoke to Jabba the Hut and played a hologram, courtesy of R2-D2, which had a recording from Luke Skywalker. In the recording, Luke told Jabba the Hut that he was leaving two droids, C3PO and R2-D2, in his care as a gift. Shortly after this, C-3PO asked himself what could be the matter with Luke, to place him and R2-D2 in Jabba's hands.