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.
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Question: Category: CURRENT EXPRESSIONS 
Clue: If you're engaging in wishful thinking, you may want to perform this type of "check"

Answer: a reality check


Question: Category: NEW MEXICO 
Clue: In 1942 this comparatively isolated New Mexico place was chosen for an atomic research lab

Answer: los alamos


Question: Category: THE 16th CENTURY 
Clue: In the 1569 Union of Lublin, Zygmunt II united Lithuania & this country

Answer:
poland