Which statement is an example of a theme?

a. ben doesn't make the basketball team on his first try, but he works hard and makes the team the next year.
b. a boy works hard to become good at basketball and is rewarded with high praise and a scholarship.
c. ben wanted to be a star basketball player, so he spent many long nights in the gym practicing his skills.
d. it's important to never give up on your dream, no matter how hard the sacrifice and struggle.