直流发电机发生端电压偏低根本原因是：①电枢绕组发生短路；②负载压降；③空载运行；④电枢绕组发生断路；⑤由于电枢反应()。
A. ②或⑤
B. ①或③或④或⑤
C. ⑤
D. ①或②或③
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定期维护镍镉碱性蓄电池时，深度放电的目的是消除()。
A. 抑制自放电，内部短路,“热击穿”
B. 防止硬化，单体不平衡
C. 容量失效，记忆性，内部短路
D. 单体不平衡，容量失效
Who may serve as the person in charge of loading and discharge operations aboard a tanker
A licensed officer who holds a tankerman-PIC endorsement
B. The pumpman who has a tankerman assistant endorsement
C. The Master
D. The bosun
While discharging a tanker，list can be controlled by ______．
A. Shoreside personnel
B. Using a center tank near the bow，discharging as necessary
C. Using wing tanks near the longitudinal center，discharging as necessary
D. Using the after peak tank，loading as necessary
实有蓄电池容量的测试遵循：①酸性蓄电池以5小时连续放电率；②机载蓄电池以1小时连续放电率；③碱性蓄电池10C连续放电率；④碱性蓄电池0、5C连续放电率；⑤碱性蓄电池0、25C连续放电率；⑥碱性蓄电池1C连续放电率()。
A. ①②③④
B. ②③⑤⑥
C. ①③④⑥
D. ①④⑤⑥
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