At what altitude does the FAA require supplemental oxygen for flight crew members when flying in an unpressurized cabin above 12,500 feet MSL for more than 30 minutes?
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A
Above 10,000 feet MSL at all times
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B
Above 12,500 feet MSL for more than 30 minutes; above 14,000 MSL at all times
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C
Above 14,000 feet MSL for more than 30 minutes only
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D
Above 15,000 feet MSL at all times