Given a context passage, generate a question from the passage such that its answer is shortest continous span from the passage.

Q: It was the last KH-2 Corona' satellite, which was based on an Agena-B. The launch of Discoverer 28 occurred at 00:01 UTC on 4 August 1961.

A: When was the launch date of Discoverer 28?
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Q: Heroes of Gaia (Chinese: ; pinyin: Yingxiong Zhi Cheng), known in the separate European version as Castle of Heroes, is a massively multiplayer online fantasy browser-based strategy game developed by the Chinese developer Snail Games and published in the United States by its U.S. publishing division, Snail Games USA.

A: Who worked on Heroes of Gaia?
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Q: Tofu and its production technique were introduced into Korea and then Japan during the Nara period (710--794).

A:
What country released Tofu?
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