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

Q: Which major river has its source at the confluence of the rivers Brigach and Breg in the Black Forest?

A: breg
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Q: Which group of the 1970's featured Tony Iommi on guitar, Geezer Butler on bass and Bill Ward on drums?

A: geezer butler
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Q: Who wrote the poem Elegy Written in a Country Churchyard?

A:
elegy written in a country churchyard
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