instruction:
Given a factoid/trivia type question, generate the topic of the question. The topic is the entity the question talks about.
question:
Who was the CBS News anchor-man known as 'the man Americans most trust'?
answer:
news presenter

question:
Which English king was married to Eleanor of Castile?
answer:
eleanor of castile

question:
What smelly element is also referred to as brimstone?
answer:
brimstone