Answer: A. impress his dad and make him proud
Explanation:
This story is from "The Lightning Thief". When they were talking, Percy confesses to Grover and told him that he was in the trip because he wanted to go and get his mom who was in Hades back.
He said he wasn't in the trip neither for the master bolt nor because he wanted to help his dad. Percy believes that he wanted his dad to be proud.