instruction:
Given a factoid/trivia type question, generate the topic of the question. The topic is the entity the question talks about.
question:
Which film was based on the story The Sentinel by Arthur C Clarke?
answer:
arthur c. clarke


question:
Who was the only boxer to win a world title without ever having a manager?
answer:
boxing


question:
Which actor links the films 'Mrs. Doubtfire', 'Dante's Peak', and 'Mamma Mia!'?
answer:

mamma mia!