instruction:
Given a factoid/trivia type question, generate the topic of the question. The topic is the entity the question talks about.
question:
Harry, Tom, Dougie and Danny are collectively known as who in the pop world?
answer:
dougie poynter


question:
Who succeeded Henry Cooper as British Heavyweight Boxing Champion?
answer:
boxing


question:
What country does China have its longest land border with?
answer:

china