In “The Tempest,” Alonso is the king of Naples who is shipwrecked.
Alonso is travelling by sea with members of his court when Prospero uses magic to raise the storm that gives Shakespeare’s play its title. The ship is not destroyed, but the passengers are separated and made to believe that others have perished. Alonso’s grief is especially intense because he thinks his son Ferdinand has been lost.
The king is not an innocent bystander in Prospero’s backstory. Twelve years earlier, Alonso helped Prospero’s brother Antonio seize the dukedom of Milan. Prospero therefore regards Alonso as one of the people responsible for his exile, though he ultimately chooses forgiveness over revenge.
The other names in the options are connected to Alonso but are not the answer: Sebastian is his brother, Ferdinand is his son and heir, Gonzalo is a trusted courtier, and Antonio is Prospero’s usurping brother. By the end, Alonso accepts Ferdinand’s relationship with Miranda and agrees to restore Prospero’s position.