On a lifeboat equipped with Rottmer-type releasing gear,turning the releasing lever releases().
A. the painter
B. the after boat fall only if the boat is waterborne
C. both falls at the same time only if the boat is waterborne
D. both falls at the same time even if the boat has not reached the water
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更换模块时,必须将模块上的()、组态开关等设置准确,以防止()或()。
在工程上习惯将作用在物体表面的单位面积上的力叫压力。
A. 正确
B. 错误
标准电气图中元件、器件和设备用图形符号的状态是如何规定的?