You will be given a trivia clue, and the category it belongs to. You should answer with the best answer that belongs in the category and is described by the clue. For consistency, answers should be in all lower cased letters.

Q: Category: GO WITH THE FLOW 
Clue: The Tigris flows into this gulf

A: the persian gulf
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Q: Category: IT'S NOT SO 
Clue: Though 4,500 miles long, it's not visible from space, as its materials are similar in color to the surrounding soil

A: the great wall of china
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Q: Category: "Z" END 
Clue: Artificial or synthetic

A:
ersatz
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