instruction:
Given a factoid/trivia type question, generate the topic of the question. The topic is the entity the question talks about.
question:
Which two brothers had hits with Cathy's Clown and Wake Up Little Susie?
answer:
cathy's clown


question:
Which biologist was known as Darwin's Bulldog?
answer:
charles darwin


question:
What was the Blue Swede's only No 1 hit?
answer:

blue swede