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:
Lexus is the luxury vehicle division of what car maker?
answer:
lexus

question:
In which war was the Battle of Brandywine?
answer:
battle of brandywine