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

[EX Q]: Which American actor and singer has joined Amanda Holden as one of the judges on the current series of 'Britain's Got Talent'?
[EX A]: britain's got talent

[EX Q]: Established in 1919, which is the world's oldest surviving airline?
[EX A]: airline

[EX Q]: Sheppey and Canvey are islands in which English river estuary?
[EX A]:
canvey island