TASK DEFINITION: Given a factoid/trivia type question, generate the topic of the question. The topic is the entity the question talks about.
PROBLEM: Although it was headquartered at Oak Ridge, TN, and the University of Chicago, what was the name of the WWII project that created the atomic bomb?

SOLUTION: nuclear weapon

PROBLEM: Who directed the film `Back To The Future`?

SOLUTION: back to the future

PROBLEM: Which pensioner is played by Caroline Aherne?

SOLUTION:
caroline aherne