C. To show examples of reasons books have been banned
We know that the author's purpose is this option and not the others because throughout the text, they only focus on giving examples of the reasons books have been banned or challenged: People object to certain books because they introduce ideas or topics with a vulgar language, others because the ideas expressed in the book do not align with their values, or because some books introduce ideas that people find it difficult to examine or to think or to talk about.
