Given a factoid/trivia type question, generate the topic of the question. The topic is the entity the question talks about.

Who won an Oscar for the music for Chariots of Fire in 1981?
chariots of fire

Who succeeded Jon Pertwee as Doctor Who?
doctor who

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?

new mexico