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

Ex Input:
Chep Lap Kok airport is located where?

Ex Output:
hong kong international airport

Ex Input:
Which popular Doctor Who villains, it was revealed in 2011, are to be given 'a rest' by scriptwriters?

Ex Output:
doctor who

Ex Input:
What is the name of the international cricket ground in Brisbane, Australia?

Ex Output:
brisbane