TASK DEFINITION: Given a factoid/trivia type question, generate the topic of the question. The topic is the entity the question talks about.
PROBLEM: Brasilia is the capital but which city in Brazil has the largest population?

SOLUTION: brazil

PROBLEM: Which former Portuguese African Colony joined the British Commonwealth in 1995?

SOLUTION: commonwealth of nations

PROBLEM: What is the capital of Bangladesh?

SOLUTION:
bangladesh