B. 500 words
Explanation: A personal essay should be no longer than 500 words because it is meant to be a concise and focused piece of writing that conveys a personal experience, viewpoint, or reflection. It should be able to hold the reader's attention and convey its message without becoming too long or wandering off topic. Additionally, many publications and contests that accept personal essays usually have a word limit, and exceeding it may result in the essay being disqualified or rejected.