TASK DEFINITION: Given a factoid/trivia type question, generate the topic of the question. The topic is the entity the question talks about.
PROBLEM: Princess Estelle, Duchess of Ostergotland, granddaughter to King Carl XVI Gustaf, became 2nd in line to what nation's throne when born in 2012?

SOLUTION: carl xvi gustaf of sweden

PROBLEM: The novels 'The Shipmaster, 'The Iron Ships' and 'The Trade Winds' by Cyril Abraham, are based on which 1970's British tv series?

SOLUTION: cyril abraham

PROBLEM: THX1138 and American Graffiti were the first two feature films directed by whom?

SOLUTION:
thx 1138