instruction:
Given a factoid/trivia type question, generate the topic of the question. The topic is the entity the question talks about.
question:
Who has taken over the TV role of Doctor Who, from actor David Tennant?
answer:
doctor who

question:
Princess Estelle, Duchess of Ostergotland, granddaughter to King Carl XVI Gustaf, became 2nd in line to what nation's throne when born in 2012?
answer:
carl xvi gustaf of sweden

question:
What is the name of the pig in Animal Farm?
answer:
animal farm