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 simplicity, answers should be in all lower cased letters.
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Question: Category: THE NATIONAL TOY HALL OF FAME 
Clue: Initial sales for it were sluggish, but demonstrations of how it walked down stairs at Gimbels made it walk off shelves

Answer: a slinky


Question: Category: IN THE TEENS 
Clue: One of these "wheelers" is a large tractor-trailer truck rig

Answer: 18-wheeler


Question: Category: HISTORIC LASTS 
Clue: In the "thanks a lot, fellas" department, Mongolia was the last country to join this group--August 9, 1945

Answer:
the allies