On open lifeboats,the purpose of the wire stretched between the davit heads is to().
A. keep the movement of the davits at the same speed
B. keep the davits from slipping when they are in the stowed position
C. prevent vibration during lowering of the boat
D. support the manrope
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232年春,蒙古军和金军在钧州以南的()进行大战,金军精锐尽失。
郭茂倩的《乐府诗集》中收录南朝乐府民歌最多的是()。
A. 《杂曲歌辞》
B. 《杂歌谣辞》
C. 《清商曲辞》
D. 《横吹曲辞》
清扫作业场所时,不得用水冲洗电气设备、()以及设备传动部件。
A. 设备底座
B. 照明
C. 信号线路
D. 电缆