解析: 第三段最后一句提到“The novel is famous for its warmth and humor, despite telling a story of innocent Tom Robinson being accused of raping a white woman because he was black.”To Kill a Mockingbird by Harper Lee讲述了无辜的Tom Robinson由于是黑人而被白人妇女起诉的故事,因此推断这部小说的主题可能涉及到种族歧视。故选C。