TASK DEFINITION: Given a factoid/trivia type question, generate the topic of the question. The topic is the entity the question talks about.
PROBLEM: In May 1940, who became British Prime Minister after the resignation of Neville Chamberlain?

SOLUTION: prime minister of the united kingdom

PROBLEM: What was Paul McCartney's first solo album called?

SOLUTION: album

PROBLEM: The Union of South Africa was formed in 1910: which area did not join the Union until 1919?

SOLUTION:
africa