What aspect of the prophecy still troubles Oedipus after the news about Polybus?

The concern that still troubles Oedipus after the news of Polybus’s death centers around the fact that his mother is still alive. He initially believed that the prophecy foretold by the oracle—that he would kill his father and marry his mother—had been fulfilled with the death of King Polybus, whom he believed to be his father. However, the revelation that his mother, Jocasta, is alive casts doubt on his understanding of the prophecy and suggests that he may still have to confront its implications. This realization reignites his fears and uncertainties about his fate, as he grapples with the potential consequences of the prophecy that he has desperately tried to avoid.