Problem: Given the question: Question: "What was the reason for being sad?"  Context: "On Children's Day, June 1, 2008, many parents went to the rubble of schools to mourn for their children. The surviving children, who were mostly living in relief centres, performed ceremonies marking the special day, but also acknowledging the earthquake."  Answer:
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The answer is:
earthquake


Problem: Given the question: Question: "Is the ground state of the Hilbert space a QED vaccum or QCD vacuum?"  Context: "In quantum mechanics and quantum field theory, the vacuum is defined as the state (that is, the solution to the equations of the theory) with the lowest possible energy (the ground state of the Hilbert space). In quantum electrodynamics this vacuum is referred to as 'QED vacuum' to distinguish it from the vacuum of quantum chromodynamics, denoted as QCD vacuum. QED vacuum is a state with no matter particles (hence the name), and also no photons. As described above, this state is impossible to achieve experimentally. (Even if every matter particle could somehow be removed from a volume, it would be impossible to eliminate all the blackbody photons.) Nonetheless, it provides a good model for realizable vacuum, and agrees with a number of experimental observations as described next."  Answer:
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The answer is:
QED


Problem: Given the question: Question: "Who revealed the information?"  Context: "Information had been kept on digital tape for five years, with Kahle occasionally allowing researchers and scientists to tap into the clunky database. When the archive reached its fifth anniversary, it was unveiled and opened to the public in a ceremony at the University of California, Berkeley."  Answer:
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The answer is:
University of California, Berkeley