Given a factoid/trivia type question, generate the topic of the question. The topic is the entity the question talks about.

Example Input: Which English king was the son of Edward, the Black Prince?
Example Output: edward, the black prince

Example Input: 'Edward Lewis' and 'Vivian Ward' were the principal characters in which popular 1990 film?
Example Output: edward lewis

Example Input: Simpkin is the name of the cat that appears in which Beatrix Potter book?
Example Output:
beatrix potter