instruction:
Given a factoid/trivia type question, generate the topic of the question. The topic is the entity the question talks about.
question:
In which constellation is the star Deneb?
answer:
deneb


question:
In which country are the Angel Falls, or Kerepakupai Ven?
answer:
angel falls


question:
What at the end of 2010 was Amazon's biggest ever selling product?
answer:

amazon.com