Problem: What replaced the Cyclops computer system, that helps to determine whether a serve is in or out, at the US Open in 2006 and the Wimbledon Championships in 2007?
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A: hawk eye

Problem: Who, in 1794, patented the cotton gin, that enabled cotton fibres to be plucked from seeds mechanically?
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A: eli whitney

Problem: Churchill went to the country in the summer of 1945 but was defeated by which Labour leader?
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A: clement atlee

Problem: What causes the sting caused by a nettle or an ant?
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A:
formic acid