instruction:
Given a factoid/trivia type question, generate the topic of the question. The topic is the entity the question talks about.
question:
Which river begins in the Rocky Mountains in south-west Colorado, crosses New Mexico and forms the border between Mexico and the USA before reaching the Gulf of Mexico?
answer:
new mexico

question:
Which two brothers had hits with Cathy's Clown and Wake Up Little Susie?
answer:
cathy's clown

question:
Who was British Prime Minister at the time of the Cuban Missile Crisis?
answer:
prime minister of the united kingdom