船员的疲劳属于职业疲劳。防止疲劳和及时消防疲劳，避免在过度疲劳情况下作业是确保船上持续性安全的必要条件之一。
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Regulations require that cargo pumprooms on tank barges (constructed in 1965) carrying grades B or C liquid cargoes have power ventilation systems which can completely change the air in （）.
A. 1 minute
B. 3 minutes
C. 5 minutes
D. 10 minute
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