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

Who composed 'Belshazzar's Feast' cantata?
belshazzar's feast

What are Proxima Centauri, Sirius A, Pollux, Arcturus and Betelgeuse?
arcturus

Actresses Virginia Cherrill, Betsy Drake and Dyan Cannon all married which actor?

virginia cherrill