instruction:
Given a factoid/trivia type question, generate the topic of the question. The topic is the entity the question talks about.
question:
Which engineer built the Menai Suspension Bridge and the Caledonian Canal?
answer:
menai suspension bridge


question:
Who plays Isobel Crawley in the UK television series 'Downton Abbey'?
answer:
downton abbey


question:
Which specific instrument did US jazz musician Bix Beiderbecke play?
answer:

bix beiderbecke