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

Which four letter word beginning with 'F' is a white crumbly Greek cheese, made from sheep's or goats milk and cured in brine?
sheep

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

Who teamed up with Rihanna on the 2012 track Birthday Cake Chris Brown, Jay Sean, Nelly, Usher?
birthday cake