工作椅最好能保证靠背倾角、座面倾角和座面高度的可调节,人长时间处于一种工作姿势时会导致肌肉迅速疲劳,因此工作椅设计的关键是?
A campus emergency ______ occur at any time of the day or night, weekend, or holiday, with little or no warning.
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