“I just don’t think your grades are strong enough to get you into Stanford, Charlene. Why don’t you shoot for the state college?” The college counselor’s office was making Charlene more claustrophobic by the minute, as she struggled to process Mr. Martin’s words. Not strong enough to get into Stanford? she thought to herself. Still in a daze, she thanked him feebly and went to meet Rhonda in the cafeteria.
“Look, you’ve still got almost a year before the application deadline,” Rhonda reminded her when she heard her story. “I’ve seen you on the basketball court. You’re a fighter, so get out there and prove Mr. Martin wrong! ”
Something in her friend’s words hit home for Charlene. Mr. Martin may be the “expert,” but he didn’t know what she had inside, what she was capable of—and neither did she. So she’d spend the next nine months discovering exactly that. Day by day, week by week, Charlene worked to excel. On the basketball court, she was all focus and determination, dazzling her teammates and winning the coach’s praise. She threw herself into her studies, but she also volunteered at an animal shelter on the weekends and became active in various school clubs. “Well-rounded” was what she figured Stanford wanted, and that’s what she intended to deliver.
The next spring, when the acceptance letter arrived on Stanford letterhead, along with a basketball scholarship, she opted against waving it in Mr. Martin’s face. The news reached him through the grapevine, and he sent her a congratulatory note. Years later, on a visit home, she stopped in to Mr. Martin’s office and thanked him for expressing his doubt in her abilities which ultimately made her work that much harder to get into Stanford.

What is the main theme of this passage?
A. The clearer one's goals are, the easier they are to attain.
B. Volunteering will make you a more well-rounded person.
C. Hard work and determination are the keys to success.
D. A lot of good can be accomplished in a short time.