Final answer:
Percy's father wrote an encouraging and loving letter to Percy at the end of the story.
Step-by-step explanation:
In the story,
- A recipe for blue cookies is not mentioned in the letter.
- A prophecy about Percy's destiny is not mentioned in the letter.
- Encouragement and love is mentioned in the letter as Percy's father tells him to remember who he is and where he comes from, assuring him that nothing can harm him.
- A warning about upcoming dangers is not mentioned in the letter.
Therefore, the correct answer is encouragement and love (c) as Percy's father sends him a comforting message of support and affection.