Final answer:
The best example of a theme is 'Be wary of rumors' because it represents a cautionary message, which is central in various stories and can be expanded into an insightful essay. Examples of stories with this theme are 'The Crucible, 'Othello', and 'To Kill a Mockingbird'.
Step-by-step explanation:
The best example of a theme in the provided options is C. Be wary of rumors. A theme is a central idea, subject, or message in a story and is usually an insight into life or human nature. 'Be wary of rumors' suggests a cautionary message about the potential harm or miscommunication that rumors can cause, which can be explored in depth within a story or essay.
It's important to remember that themes are about the bigger picture and what the reader takes away from it beyond the specific events or characters in the narrative.