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

Ex Input:
'Bring It All Back' was the debut single for which group in 1999?

Ex Output:
bring it all back

Ex Input:
Which analgesic drug, first isolated in 1804, was named after the Greek god of dreams ?

Ex Output:
analgesic

Ex Input:
Zeus' visit as a swan to whom resulted in the birth of twins Castor and Pollux?

Ex Output:
castor and pollux