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

Ex Input:
Which English king was the son of Edward, the Black Prince?

Ex Output:
edward, the black prince

Ex Input:
What is the alcoholic ingredient of a Screwdriver cocktail?

Ex Output:
screwdriver

Ex Input:
What is the official language of Barbados?

Ex Output:
barbados