产生静电的原因主要有摩擦、压电效应、吸附带电、（）等。
A. 通电
B. 感应起电
C. 两种不同物体分离
D. 接触
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In stopping distances of vessels，head reach can best be described as the（）.
A. difference between the vessel's speed through the water at any instant and the new speed ordered on the telegraph
B. distance the vessel has actually run through the water since a change of speed was ordered
C. distance the vessel will run between taking action to stop her and being stationary in the water
D. speed at which a vessel should proceed to ensure that she will run a predetermined distance，once her engines have been stopped
气体灭火系统模拟喷气试验结果应符合下列规定（）。
A. 延迟时间与设定时间相符，响应时间满足要求。有关声、光报警信号正确。有关控制阀门工作正常。
B. 信号反馈装置动作后，气体防护区门外的气体喷放指示灯应工作正常。
C. 储存容器间内的设备和对应防护区或保护对象的灭火剂输送管道无明显晃动和机械性损坏。
D. 试验气体能喷入被试防护区内或保护对象上，且应能从每个喷嘴喷出。
钳工的主要工作是加工零件、装配、（）、工具修理和制造。
A. 改进工艺
B. 改进设备
C. 设备维修
D. 检测设备
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