It is said that Apollo spoke through his Priestess, who was commonly known as Sibyl. This title has changed into （  ） after Apollo slew the monster.

In Delphi all Greeks go to a temple of a god for oracles and they asked the god for advice or prophecy. A priestess would give an answer on behalf of the god which called an oracle. What is the god? A: Apollo B: Zeus C: Helios D: Athena