TASK DEFINITION: Given a factoid/trivia type question, generate the topic of the question. The topic is the entity the question talks about.
PROBLEM: Which major river has its source at the confluence of the rivers Brigach and Breg in the Black Forest?

SOLUTION: breg

PROBLEM: Which two brothers had hits with Cathy's Clown and Wake Up Little Susie?

SOLUTION: cathy's clown

PROBLEM: Bobby Cox was manager of which US professional baseball team before his retirement in 2010?

SOLUTION:
bobby cox