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

Example Input: Mar Chiquita (Cordoba) is the largest natural salt lake in which South American country?
Example Output: mar chiquita lake

Example Input: Brasilia is the capital but which city in Brazil has the largest population?
Example Output: brazil

Example Input: Which country is bordered by China to the north, Laos to the northwest and Cambodia to the southwest?
Example Output:
china