What is the origin of they (singular)

The Oxford English Dictionary traces singular they back to 1375, where it appears in the medieval romance William and the Werewolf. Except for the old-style language of that poem, its use of singular they to refer to an unnamed person seems very modern.

Explanation: The singular they emerged by the 14th century, about a century after the plural they. It has been commonly employed in everyday English ever since then and has gained currency in official contexts.

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you have to either add a photo or put them answers in with the questions

answer; /// the correct answer to the above statement is (a) because of the decline on native american labor forces;