In "Perseus and the Quest for Medusa's Head," why is Perseus charged with the task of bringing the king the head of Medusa?

AThe king wants to rid the kingdom of the evil villain.
BPerseus suggests this task, and the king agrees to shame Perseus.
CPerseus wants to marry a queen from across the sea, and this is the bride price.
DThe king's daughter is angry with Medusa and asks Perseus to slay her.